Username:

Password:

Altair AstroDIO DehumidifiersAtik CamerasModern AstronomyDavid HindsNe3 Filters
Solar Gravity 2018

Author Topic: PHD (1 and 2) perfect straight line, but star trails for some objects  (Read 8571 times)

0 Members and 1 Guest are viewing this topic.

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Giancarlo

I still think the trailed stars is predominantly a mechanical issue. Any chance of posting an image of your imaging setup showing how everything is fitted together.

Chris

LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Hi Chris,

I have pictures...still on the EQ5, now I have the HEQ5 but connections are the same. I tried as well yesterday tiding up cables around the mount and leaving them free...being light and not many did not change anything, I always check they're free to go.










This is the miniguider, attached to the finder shoe on the scope, all tightened up and really not moving...


AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
I would put money on it being some play somewhere in the finder/shoe/dovetail. We are talking a handful of acrseconds and that is very hard to "feel'. There is nothing in the guide graphs that explains trails of those lengths (though worth download PHDLab to study the full guide graph for an image cycle) so it is a movement in either the imaging scope relative to the guide scope or vice versa.

Chris

ps do you image from that decking?
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Uhhmm interesting, well I should be able to test soon hopefully guiding on the dovetail with my WO66 (clamped directly on the top dovetail through its dovetail base to avoid any flexture), before spending more money ordering another guiding system before I'm sure the problem lies there and not mirrors.

Like you say I can't see a big relation between the graphs and those trails, considering they appear just sometimes, mostly when imagine objects more down the horizon (around 30 degrees). I struggle understanding how this is visible only sometimes, but never had such problem so I'm not expert.

My only worry is that could be again another mirrors problem...if I cannot spot/feel such small movement then I have no way of being sure or spot it moving around with Glatter laser, because to my eye the laser beam stays firm and folds back always in same place. Obviously if I grab the focuser and push it around then I can move slightly the whole thing (laser/focuser/primary), but I have to apply some force.

And yes I image from the deck, I have those 'holders' on it positioned to align roughly the mount and then I adjust it with hour discs/PolarAlign/polarscope. It's positioned where the deck is on its supports, so unless I walk there (obviously) it doens't move and honestly never had a problem. When imaging M13 and Ring yesterday it was also quite windy and there was no sign of movement or trail or problems guiding (nor I ever had them before from same deck with a 9kg OTA + accessories on my old EQ5).

In theory any movement in the deck anyway should involve everything and so if minimal then guiding could solve it? From what I understand here is difficult to understand because there's no correlation between guiding/graph/trails and it doesn't happen in every position...so yes surely it seems something mechanical.
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Just a thought but are the lock screws on the primary fully tightened up?
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Chris....that's a good question.

The short answer is: I 'think' so. I say 'think' because I have a question about it that I wanted to ask: before collimating it, I was always scared and not sure what screw to move first, because sometimes one doesn't move until I move the other in the opposite way before, and some other times one moves and then I move the other in opposite direction. All till I feel they are tight enough, but is not easy without altering it all. On secondary is much easier and it feels much more sturdy and 'in place'.

Said that I'm not very good with DIY and similar, so I'm a bit confused about what you call 'lock screw' and the 'push pull' definition, although I've seen many links with the whole thing dismantled I still get confused.

Long question short: which one is the 'lock' screw? The pull (big silver one) or the push (black smaller one)? And what's the best way I can check that primary is well locked without creating too big mess? :) (I still have the Glatter holographic circles).

Chris I hope to see you at Kelling on the Saturday and that you'll have time for a beer, is the minimum I can do for all your help!


P.S. I'm not giving up on this scope..I love so much the images from it (when not too low on horizon and in the center 65% of the FOV) that I want to improve it to use it fully. I'm waiting for the AT2FF field flattener (without focal reducer) and the CCDT67 focal reducer, both good for GSO 6/8RC, to see if I can improve field at its native focal and also if I can correctly use the reducer to have a faster scope with shorter focal length when needed. And being all compatible with the RC8 is all good for my upgrade plan :)
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
https://www.astronomics.com/documents/astro%20tech/astro-tech%20at6rc%20collimation%20sheet.pdf Might help if you have not seen it. I don't think that the collimation screws on these are a true push pull. As far as I know the small black ones do the adjustments and after collimation the larger silver ones should be snug tight to lock that in. I'm not quite sure of the mirror cell arrangement on these scopes but some degree of mirror shift may well fit in with what you are seeing when imaging at lower altitudes. I would, however, expect any shift to happen only in the first sub or two and for the primary to find its own support again. No harm in trying it though as it would be a simple solution. No need to take a wrench to the lock screws as over tightening may distort the mirror cell. Just snug tight should be enough.

Chris

ps Interestingly I also came across this http://www.cloudynights.com/topic/486239-at6rc-mirror-flopyes-mirror-flop/
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
That thread is very interesting...it connects well with this page I linked before http://deepspaceplace.com/gso8rcpointing.php but is scary as hell..I think I get it, it doesn't seem to difficult to just take out the rear cell.

I will first check if the locking screws are well tight (not too much!), if not then I'll tight up those and I'll check if solves the problem. I can also probably check if mirror moves without dismounting everything: with a long stick and a soft end, touching the mirror on border and seeing if it shifts in its place..if it does then I'll disassemble it and tight the holder.

As you said I would expect anyway to not last forever if it's a shift, at some point it should find its position...and this leads to TWO IMPORTANT CLUES:

1) when I noticed for the first time this problem on M101, I remember I got a full series of 10 300s exposures and the stars trail was diminishing after each sub...always there at the end of the 10 subs, but noticeably less sub after sub

2) first time I imaged M101 with this scope was first night out of box, no collimation done by me, and indeed I got 10 subs 300s that were 'perfect', and on the EQ5 and using same guiding system I use now (screenshot below). That would lead to something that changed after collimation and so to possible lock screws to be checked?

AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
 :scared: HOLY COW  :scare:

Well...one of the locking screws was not as tight as the others...I tighten it up...then tried to test mirror flop...long stick with a soft tip at end...touched side of the mirror where there's no reflection coating...AND MIRROR MOVED!

So...well whatever let's dismount this thing and shake the back to see if mirror moves...and I OPENED IT  :big_clap:



And you know what? Shaking the back I could HEAR and feel the mirror move! So I did what was suggested on that CloudyNights link you sent..unscrewed baffle, loosen locking screws on the o ring holding the mirror, tightened it a bit, tested the shaking (ight shaking) was not moving mirror anymore, re-locked the small locking screws for the o ring, screwed again the baffle...everything closed back nicely..

What the f.....well now collimating again with Glatter and later will try a quick primary collimation to test if the guiding is now good..anyway was something needed to do. Might improve collimation as well!
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
For anyone reading..I'll add it to other topic about RC/collimation once all verified, but indeed disassembling that little scope is VERY simple..I'm barely able to change a lightbulb and I found it easy :)

But I have a good experience with music instruments..so maybe that helped.

Anyway, reassembled it all back, checked collimation, visually was as 'imperfect' with Glatter as it was before. Did not change much. But mirror touched with my stick now doesn't move, and whatever movement then it goes back to its position.

I decided that maybe this mirror not very firm in its cell was also what causing the Glatter collimation to be so far off once outside with a star test (where obviously focuser/camera moves around). Also to be noticed something I did not know: the mirror IS HEAVY. Meaning that it takes a lot of gravity, so it needs to be very stable in its cell indeed.

So I decided anyway to retry a proper collimation, moving only primary I was able to center the Glatter holographic circles AND at the same time the laser beam folded back on itself automatically...must be a good sign:





It stays in the same place also when not pointing it to the floor but to a wall and locked into the focuser.

So....was useful anyway to learn how this thing is done and be less scared..and let's hope it helps both with collimation AND the guiding :)
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
As easy as stringing a guitar!

Fingers crossed, should be clear here later so you may get to test it yet.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Uhhm well stringing a guitar is much simpler, even if indeed it can be demanding sometimes  8)

So...first report in the hour I got of clear skies...waiting hopefully for more:

1) collimation situation did not change compared to before: still out of Glatter is not good and needs primary and secondary adjustements putting off the Glatter. Anyway in 30 minutes I put it back on track, still to be perfected but good

2) guiding....EUREKA! I just had time to slew to M101 (around is just out of field), engage PHD, calibration, 2 minutes to settle down and then a single 300s exposure (below the PHD run of the imaging, quite good with error -+ 1" and a not so aggressive/rough guiding - crop 1:1 of the 300s central FOV)





Now...if I get some more clear skies I'll do more in that same region that was problematic, and another one just to confirm...if so it means that tighening the primary in its cell so it doesn't wobble solved the problem of guiding.

First image is promising...nice guiding, nice round stars..more if/when I get clear sky :)
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9638
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Tremendous news Giancarlo. Just testing a few things myself in preparation for Kelling and then the new season.

this is my current guide graph at around 4"/pxl guider scale cf 1"/pxl image scale i.e. 1:4  :D
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo
Samyang 135mm f1.8

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Wow!

What do you use for that analysis? I might be interested :) Jealous for Kelling...will try some last minute booking, I don't even care about the tent I need the pitch :D

I ran another batch of images as well here...EUREKA! Solved, is official...guiding is good, and images perfect where yesterday there was star trail!

So it's official...basically all the AT6RC and 8RC have primary too loose for effective guiding...but is simple to fix. And thanks to your suggestions I adjusted guiding parameters and is now much smoother, it corrects less. Below crop 1:1, pinpoint :)

I'm seriously envious of that guiding you have there...oh well...time to go out again with a beer and try improving again a bit collimation..waiting for the FF and the focal reducer to see which one works better :)

At Kelling even if it will be the day I'll be curious to see your setup and learn some more :)



AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
VICTORY!

On the whole front, I solved the problems just disassembling the damn thing and fixing that primary mirror!

Look at the Vega pic I just took...I adjusted the secondary mirror with much more success than before, probably the primary was moving making also collimation quite hard.
This is BY FAR the best collimation I ever had...this is an uncropped full frame (here full res http://cloud.thebenchmusic.com/uploads/Img0718.JPG), no field flattener and no reducer:



I'm now eagerly waiting for the field flattener, if it can improve things even more.

I'll add tomorrow further instructions to my procedure on the other topic. For the first time I feel I'm mastering this instrument  8)
AA 8" RC + AT Flattener, SW Esprit 100 + SW Flattener, Daystar Quark Chromosphere
Canon 6D modded, Nikon D750 unmodded, ASI174MM-COOL, SX Lodestar X2, ASI120MM
Canon & Nikon various prime lens
SW HEQ5 Rowan Belt Mod, AA 60mm Guidescope, Astrotrac, SW Star Adventurer
Mac 15" Retina Parallels: EQMOD, PHD2, SGP, PlateSolve2, BYN, CDC, Pixinsight, Photoshop
William Optics binos, Baader Hyperion eyepieces, Meade & Celestron binoculars
http://theski.es

 

ukbuysellRemote Imaging from AustraliaSharpSkyblank APTUKAI on Facebook
TinyPortal © 2005-2012