Wide field Gear

[Kenza]

Hi! I am thinking of doing a bit of wide field imaging. I have three canon lenses (telephoto, wide angle and a standard prime lens), I have a good tracking mount and I have a Canon 7D Mark II Unmodified camera.

I also have an Atik 4000 Mono but unfortunately wide field setup with this CDD and a canon lens won't come to focus (because of the filter wheel) so I have given up on the idea. Should I buy a color CCD or just use the unmodded 7D?

Also, is it necessary to guide wide field shots or will good polar alignment and tracking do the job? I have a lodestar guide cam which I use with an off-axis guider on my scope but how am I supposed to use it with just the camera and lens mounted?
 

 

[wimvb]

If you want to include Ha emission nebulae in your images, a modified camera will give you better results. Otoh, some unmodified cameras are good at picking up Ha. Test.

The shorter focal length you use, the lower the requirements for accuracy in tracking. For the telephoto lens you may need guiding if you want long exposures. Generally, you should be able to get exposures of a few minutes with an unguided wide field setup, if you have accurate polar alignment and a balanced rig with little periodic error. In the end, you will have to judge how much star trailing you can live with.

Imo, more important is the quality of your lenses. If you get distorted stars and/or chromatic aberration, this can be more disturbing than trailing stars.

Hope this helps somewhat,

 

[StargeezerTim]

I would personally miss my modded dslr for wide field. You will need an intervalometer, about a tenner!

I find I can get 5 or six minutes unguided up to 150-200 mm so guiding is not really necessary. You may need a clip filter for lp or a uhc filter, depending on lp where you live.

Personally, i love widefield imaging. it is easier and quicker to set up and satisfying to see what you can achieve from ordinary gear...

[hjw]

Hi Kenza,

my first choice for widefield is and would be the prime lens. Slightly stepped down it gives a very sharp image corner to corner. The precision of the polar alignment is dependent on the focal length of the lens. With the 50mm lens I do not require polar alignment... To clarify, I have the leg positions of my mount marked with metal rings and get within ~2 arcmin of polar alignment without adjustment.

3 minute subs stacked gives images like this:

By the way, my camera is not modded either.

Good luck!

HJ

[Kenza]

Thanks for the advice, i found it very useful. 

@hjw i had no idea unmodded cams could make such images. Great pics by the way!

i have decided to image with the unmodded 7d. I know that prime lenses would be better but my 70-300 L is pretty versatile (i can shoot both wide field and say M31). And of course i already have it, so why not use it. In case of m31 i would have to guide probably. I was then thinking of a dual saddle for the camera and guidescope. Would that do the trick?

[StargeezerTim]

13 minutes ago, Kenza said:

Thanks for the advice, i found it very useful. 

@hjw i had no idea unmodded cams could make such images. Great pics by the way!

i have decided to image with the unmodded 7d. I know that prime lenses would be better but my 70-300 L is pretty versatile (i can shoot both wide field and say M31). And of course i already have it, so why not use it. In case of m31 i would have to guide probably. I was then thinking of a dual saddle for the camera and guidescope. Would that do the trick?

I use the 70-300L and it is a fabulous lens for widefield.

I use a dual saddle when i guide so, yes, that would do the trick!

[wimvb]

On 2016-11-15 at 21:25, hjw said:

Hi Kenza,

my first choice for widefield is and would be the prime lens. Slightly stepped down it gives a very sharp image corner to corner. The precision of the polar alignment is dependent on the focal length of the lens. With the 50mm lens I do not require polar alignment... To clarify, I have the leg positions of my mount marked with metal rings and get within ~2 arcmin of polar alignment without adjustment.

3 minute subs stacked gives images like this:

By the way, my camera is not modded either.

Good luck!

HJ

Great images, those. It seems that unmodified Pentax cameras are quite good at picking up Ha, better than Canon.

Sensitivity in Ha is very much dependent on camera make and model for unmodified cameras.