Username:

Password:

Altair AstroDIO DehumidifiersAtik CamerasModern AstronomyDavid HindsNe3 Filters

Author Topic: TS Field Flattener CCD to Lens Distance  (Read 12036 times)

0 Members and 1 Guest are viewing this topic.

Offline rofus

  • Full Member
  • ***
  • Posts: 365
  • Astrophotography between a song and an album
    • The Ski.es Astrophotography Gallery
Re: TS Field Flattener CCD to Lens Distance
« Reply #15 on: 17:17:57, 04 September, 2015 »
Waiting for my AT2F field flattener for my F8 RC8...this chart is going to be very useful to verify setting with my Nikon! Thanks.

Anyone knows if/how to use the FF together with the CCDT67 to make the flattest possible field and make the RC8 a bit more wild and fast? How to deal with distances if the two are together?
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 Nomis Elfactem

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 13004
    • The View From A Room
Re: TS Field Flattener CCD to Lens Distance
« Reply #16 on: 17:23:32, 04 September, 2015 »
Rufus, treat it with a bit of caution as the error bar is quite wide (I build it off info on a retailers website not on TS specification data) and on some scopes that will be the difference between it working and it making things worse ;-)  Nothing beats the old "trial and error" approach, as long of course you have a good supply of different sized spacers to test different combinations !

Good luck
S.
Simon

Scopes: Astro-Tech AT-111EDT Triplet, TS65ED Quad, Orion ST80, Modded PST-90 Solar Scope, PST Cak (on loan)
Cameras: SXVF H694, Atik 16ic, Canon EOS 600d, DMK41, DMK21, QHY 5L-II (mono & colour)
Accessories: SX USB Filter Wheel, SX OAG, Baader LRGB Ha SI OII Filters, SharpSky Focuser
Mount: EQ6 (EQMOD), SW Star Adventurer, plus a lot (and I mean a lot) of other bits and pieces

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 9682
  • If at last you do succeed, don't try again
    • Rosemount Observatory
Re: TS Field Flattener CCD to Lens Distance
« Reply #17 on: 17:34:40, 04 September, 2015 »
I would be very surprised if you can use them both at once successfully!!!

I found the CCD67 on my 10" RC to have a degree of field flattening ability though I set the spacing to give a reduction of around 0.8 so nothing too mad. That gave it a focal ratio of about 6.5 which seemed to work very well.

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
Re: TS Field Flattener CCD to Lens Distance
« Reply #18 on: 17:56:14, 05 September, 2015 »
Thanks I'll try all the various options...I'd like to do as Chris said so having the CCDT67 reducing 0.85 and not 0.65, I have three spacers so I'll try starting from the 46.5 of Nikon ccd/front distance plus the t2 adapter and the noses :)

I don't want it reduced too much but to have it a bit faster would be good, so if the 0.85 works and makes field flatter then I'll go with it...if the AT2FF instead gives me an even flatter field, I'll go for that :)

I also got a ST80 for guiding more precisely, testing awaiting clear skies as usual!
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 altairastro

  • UKAI Sponsor
  • Full Member
  • *****
  • Posts: 455
  • Keep looking up.
    • Altair Astro
Re: TS Field Flattener CCD to Lens Distance
« Reply #19 on: 15:36:08, 02 December, 2015 »
I do find it incredible that FF's are designed for very precise spacing to chip over a narrow range of FL and yet the manufacturers struggle to provide such key information. I have had the devils own job getting W/O to give the spacing for their TMB FF for FLT as all their charts used to show the distance from the crown point of the FF lens that is pretty hard to measure from. After numerous emails they then showed a measurement from the back of the T adaptor.I have 3 of them and they are all different so a totally useless pice of information. When finally they come up with the distance from the back of the T mount plate their suggestion is an optimum of 54.98mm for the FLT110. 54.98mm mind not 55mm. That is now on their latest offering on the W/O website. 54.98mm is pretty definitive. Try measuring that with a ruler let alone finding a T spacer to 0.2mm of accuracy.


Simon. I wholeheartedly agree in terms of a general purpose FF but my W/O example is very scope specific. W/O simply failed to understand that giving a spacing measured from the crown of a lens that is all but inaccessible is not very helpful! Took a year of emails for them to finally grasp what I was trying to get at. My, albeit limited, experience in the use of FF's is that the lens to chip distance is very critical for some FF's. With my W/O TMB FF a couple of mm makes a huge difference when measured with CCD Inspector. I bought the thing to get a flat field, not a curvy one! As you say, FF manufacturers are clever people and should be able to provide guidance along the lines of the chart you have produced. These are not cheap items and giving users the data they need to use them is not asking too much.


Yes true Chris, they should provide the info (if they know it) but they need the lens design model in Zemax and the focal reducer or flattener design also in Zemax. Then they need combine these elements into a single system for the optimum spot size to work it out. And you also need to take colour correction into account over a set spectral range. It's actually quite a lot of work and can only be done by experts. So if the flattener is made by a different company, and you have a generic one, then it's a little hit and miss with all the experimentation that comes with it. Hence why we have comprehensive charts on the Altair Astro website for our compatible OTAs, and have done for many years (:nerd:).



Simon, what kind of real world results did you get with this setup how was the colour correction and coma?
Altair Astro
Retailers, manufacturers and distributors of fine astronomical equipment.

 

ukbuysellRemote Imaging from AustraliaSharpSkyblank APTUKAI on Facebook
Powered by SMF 2.0.15 | SMF © 2006, Simple Machines LLC
DarkBreak by DzinerStudio. Theme modified by The UKAI Team

Page created in 0.148 seconds with 36 queries.
TinyPortal © 2005-2012