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Author Topic: North America Nebula region wide field - superfast narrowband first light  (Read 80 times)

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Offline chris.bailey

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I have been playing around with various camera lenses with limited success so bit the bullet and got a Samyang 135mm f2 manual lens, based on positive reviews on it for astrophotography. The big downside of it is the lack of back focus compared to 6x7 large format film lenses. As such with a Geoptik adapter its limited to having a single filter within the adapter so it just had to be the 3.5nm Ha filter. Reports suggest that nailing the correct back spacing is pretty critical so I spent a couple of hours faffing with Delrin spacers and even had to sand one down to get it right. There are some BIG Sharpless objects that this will work well with so with a bit of clear sky I gave it a test.

Focusing manually at f2 is a lesson in frustration but to motorise it will take a high resolution planetary geared stepper motor. I don't think I totally nailed focus but you just can't turn the focus wheel manually by such small amounts. f2 really sucks in the photons so even with 30 second test exposures, things were pretty visible. 6 minute subs grabbed photons by the bucket load so for the faint objects 10 minute subs should do the trick nicely. I didn't get a chance to run a sky model so this is 6 minute unguided subs with just PEC running. A moderate sky model should improve things further. The field is reasonably flat and corner to corner illumination is good. I just used Bias frames (no darks or flats) but did apply a big 8" dither. I don't have a counterweight light enough to balance such a light setup so had to improvise with a couple of weights from bits box!

I have to say I am impressed. Its not a cheap lens but the optics look good and there isn't a telescope that gives such a wide field of view. I think it is going to be some fun, if the weather starts to co-oprate.

Imaged: 12th October 2017
Mount: Paramount Mx
Scope: Samyang 135mm f2
Camera: SX814 3.5nm Ha filter
Guided: Unguided
Exposures: 19 x 300
Image Scale: 5.68"/pxl
Captured: SkyX
Processed: Pixinsight
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

Online Nimbus

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Super job Chris and as you say a massive fov! The critical focus zone must be tiny so you may have to put your project hat back on and build a system for electronic focusing.

However, once you have any easier focus system this looks just the job for those ultra faint Sharpless object you like to image. Best of luck with the current season.

ATB Jim
EQ8 Pro
TAK FSQ 106 EDX4
ATIK 16200 Mono & Lodestar OAG, EFW2 2" Filters
Focusmax4, Robofocus
Maxim DL6.13, CdC & Photoshop CS3E,

Offline chris.bailey

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...The critical focus zone must be tiny so you may have to put your project hat back on and build a system for electronic focusing...

Thanks Jim. Field of view is 5.3 x 4.3 degrees which is great for the larger objects. CFZ is about 10 microns in Ha so yes, pretty small indeed. I have just got a planetary geared NEMA 17 stepper motor with 5700 full steps per revolution and with a timing belt up to the lens focus wheel that gives about 50:1 thats 285,000 steps per revolution of the focuser wheel. If needs be I can micro step that 1/2 or even 1/4 so that should be more than ample. Controller electronics are all laid out on my workbench, just need soldering and boxing up. There is also a very slight left to right tilt but I have the mechanism in place to fine tune that too. Just hope the weather co-operates to make it worthwhile!

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

Offline Nomis Elfactem

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That's a doozy Chris.

Would love to see some pictures of the focus controller and set-up !?!

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

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Si

This is how I have it setup. The Samyang 135 is quite a heavy piece of glass so I have added a guide scope ring at the front to give some support (this will also fine tune any tilt).

Focus controller is an Arduino Nano and an 8825 EasyDriver board running myFocuserPro minimal setup https://sourceforge.net/projects/arduinofocuscontrollerpro/, which I thoroughly recommend. Ascom focuser setup for about £40 and £30 of that is the motor and bracket!

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

Offline Malcolm L

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a fantastic awesome image , love your setup :big_clap: :thumbup:

Offline bobscott

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Great set up Chris and a very nice sharp detailed image your on a winner there. I have received a F2 lens from a friend who has packed in imaging it is all set up in a home made configuration to connect to my ccd camera via a Crayford focuser with a wooden box in between I have never done wide field imaging so it will be a steep learning curve for me but I will try and see if I get any results I was thinking of fitting my QHY8 Pro OSC camera on it as it is a bit simpler to use than the mono cameras.

Bob
Celestron cpc 11",william 90 megrez pro EQ6 EQMOD, QHY5 cam,philips SPC900,canon 400D modded QHY8 Pro
QHY9m

 

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