Imaging With My 102

[Sunshine]

Hello imagers, I won't bombard you with a myriad of questions expecting you to turn me into an expert overnight, having said that, I have two options for getting started in imaging and would like to know which you recommended. My mount is a Vixen GP with one axis motor (no goto) which i have had great success in accurately polar aligning in the pas to keep objects dead centre for minutes at a time, having said that, I wouldn't be engaging in exposure longer than tens of seconds at the most to keep error to a minimum. Although I have never images DSO's, I do understand many of the challenges involved with minimal equipment and, the importance of dark skies, balancing the scope well, etc. Being realistic about my goals I do realize this is a learning curve and, I will surely be investing in better equipment in the future.

1. Using my Tak 102 with a DSLR which may require a whack of horrendously expensive Tak flatteners/adapters (are there adapters and such made other companies which will work as well to avoid buying specifically Tak?)

2. Using my 102 with a dedicated AP camera.

3. Investing in a small 70mm lets say, triplet specifically for SLR or dedicated camera.

Thanks for your advice fellow SGL friends!

Edited March 13, 2021 by Sunshine

[MartinB]

I would strongly recommend sending an email to FLO regarding flatteners/adapters with your 102.  Your message will reach the eyes of Ian King who will give you all the information you need.

In my early imaging days I used an ancient Vixen super polaris.  The polar scope was extremely good.  The gears were very good with quite a low periodic error.  The main problem I encountered was controlling backlash, it was a fine balance between excessive slop and binding gears.  This didn't present any problem until I started trying to guide.  With a short focal length scope you should easily be able to manage unguided 2 minute subs and could, possibly extend that to 5 minutes especially if using a small 70mm frac.  You might also consider a camera lens for your DSLR.  There are some superb images being produced by SGL members using a 135mm F2 Samyang lens.  This is a fast lens with superb optics (better than the Canon F2 135mmL).  It is fully manual which is perfect for imaging and drops the cost of the lens significantly.

Regarding dedicated cameras, CMOS would certainly be the recommendation over CCD if you are imaging unguided since they have a lower read noise which means you can use shorter exposures.  My advice was always to go for mono cameras but this is no longer so clear cut with the current batch of sensitive one shot colour cameras and the dual pass narrowband filters.  In fact, for simplicities sake OSC with one of these filters is exactly what I would recommend.  The only question then is the size of your chip/ price you are willing to pay.  A smaller chip has the benefit of being easier on the optics rerding being able to achieve a good flat field.  It might be better to stick with your DSLR initially to see what sort of star issues you have in the corners before making a significant camera investment.

[ollypenrice]

I can only admire Martin's answer above, which represents exactly my own thinking as the technology evolves.

Olly

[Sunshine]

9 hours ago, MartinB said:

I would strongly recommend sending an email to FLO regarding flatteners/adapters with your 102.  Your message will reach the eyes of Ian King who will give you all the information you need.

In my early imaging days I used an ancient Vixen super polaris.  The polar scope was extremely good.  The gears were very good with quite a low periodic error.  The main problem I encountered was controlling backlash, it was a fine balance between excessive slop and binding gears.  This didn't present any problem until I started trying to guide.  With a short focal length scope you should easily be able to manage unguided 2 minute subs and could, possibly extend that to 5 minutes especially if using a small 70mm frac.  You might also consider a camera lens for your DSLR.  There are some superb images being produced by SGL members using a 135mm F2 Samyang lens.  This is a fast lens with superb optics (better than the Canon F2 135mmL).  It is fully manual which is perfect for imaging and drops the cost of the lens significantly.

Regarding dedicated cameras, CMOS would certainly be the recommendation over CCD if you are imaging unguided since they have a lower read noise which means you can use shorter exposures.  My advice was always to go for mono cameras but this is no longer so clear cut with the current batch of sensitive one shot colour cameras and the dual pass narrowband filters.  In fact, for simplicities sake OSC with one of these filters is exactly what I would recommend.  The only question then is the size of your chip/ price you are willing to pay.  A smaller chip has the benefit of being easier on the optics rerding being able to achieve a good flat field.  It might be better to stick with your DSLR initially to see what sort of star issues you have in the corners before making a significant camera investment.

Great advice, thank you, my expectations for imaging with a Vixen GP with one axis motor is not stellar, I am just curious to know if it would be possible to capture very short subs in the seconds range on a bright target like M42. In the past I have had good success with accurate polar aligning by way of using an app to find the exact spot Polaris should be placed within the target reticle in the polar finder. This has allowed me to switch the motor on and keep a target centered for minutes at a time with minute manual correction as it tracks. 
 

This sort of got me wondering about maybe trying out a bright DSO, for example, I leveled my tripod and placed Polaris in its correct spot for a particular hour and after I managed to keep M42 dead centre (it seemed to me) within the FOV. It made me think of the possibility of doing very short subs with some kind of camera. Sure, dead centre to my eyes does not mean dead centre when trying to capture stars as points but, I can try with what I have.