focal reducer then barlow, or niether for photo's

[BlackWidow (Mardy)]

Just some help with this one please. Just started using my QHY8 for taking pictures. First light was had with very bad results. I need to get my focus correct and now I understand the processing a little better (getting colour) I am ready for the next step.

Apart from the fact that my image was out of focus and under exposed (I could only see the red of M8) I am happy with the guiding and location of the target. It has taken me near a year to get to this stage.

I was not happy with the image size (too small) and an using an F10 LX200GPS with a 6.3 focal reducer. I would like to get the image closer and wanted to know if I am better to remove the focal reducer putting the scope back to F10 (Slow and longer exposure)? Or am I better to keep the scope at F6.3 and add a 2" barlow to get a closer shot?


I am sure as some point all this is going to come together and I am going to get the results. Starting from no knowledge of this hobby and doing this on my own I am happy the I am getting close. I could use my Canon DSLR and get better results in the short term, but I really want to learn to master the CCD..

Any assistance would be a great help.


Regards
Mardy

[multiweb (Marc)]

Originally Posted by BlackWidow

Just some help with this one please. Just started using my QHY8 for taking pictures. First light was had with very bad results. I need to get my focus correct and now I understand the processing a little better (getting colour) I am ready for the next step.

Apart from the fact that my image was out of focus and under exposed (I could only see the red of M8) I am happy with the guiding and location of the target. It has taken me near a year to get to this stage.

I was not happy with the image size (too small) and an using an F10 LX200GPS with a 6.3 focal reducer. I would like to get the image closer and wanted to know if I am better to remove the focal reducer putting the scope back to F10 (Slow and longer exposure)? Or am I better to keep the scope at F6.3 and add a 2" barlow to get a closer shot?


I am sure as some point all this is going to come together and I am going to get the results. Starting from no knowledge of this hobby and doing this on my own I am happy the I am getting close. I could use my Canon DSLR and get better results in the short term, but I really want to learn to master the CCD..

Any assistance would be a great help.


Regards
Mardy

Your image scale should be 1.3 vs. 0.8asp with the focal reducer. 1.3 isn't bad at all. 0.8 will be more challenging to guide. Aren't you happy with the details you are getting or the size of your FOV? The QHY8 is a big sensor already. If you want more FOV you'll need a scope with a lot less FL like a newt or refractor.

[BlackWidow (Mardy)]

Thanks Mark. I am not fully sure I understand what you are telling me (sorry). so am I better to use the focal reducer and use a barlow, to get a closer image than I am getting with only the focal reducer.

Or am I better to remove the focal reducer and put the scope back to F10, which will give me longer exposure times.

I am trying to get a narrow or closer field of veiw.

Regards
Mardy

[multiweb (Marc)]

Ok then just get the reducer out and you'll get 2m FL. If you want to go closer you can barlow but at 4m FL you'll need some kind of AO.

The focal reducer will shorten your FL x.63 so from 2m to approx 1.2m resulting in a wider FOV which is not what you want.

A barlow will increase your FL thus reducing your FOV which is what you want to achieve.

The less glass in the imaging train the less light scattering or reflection, the better.