5 replies to this topic

[Sky King]

With the D750, unmodified and the D5300, Ha modified, I wanted what would give me the largest field of view. I have the Askar FMA135, but it is limited to APS-C cameras. My FRA300 says it will do full frame,

 

"With a 60mm triplet objective with an ED element and a two-element corrector, this f/5 scope has a focal length of 300mm and makes an ideal instrument for capturing stunning wide-field images of the deep sky over a 44mm full-frame image circle."

 

Unfortunately the Askar FRA300 has limited back space for a DSLR, so no room for a filter drawer. From the manual:

 

 

There was a way to mount a 31mm filter in an adapter inside the camera adapter ring:

 

 

The 31mm filter was not good as it reduced the flow of light to the camera and resulted in vignetting.

 

Next issue: The CCD Suitability Calculator says this scope needs a smaller pixel size, significant under sampling. 

 

And the D750 as unmodified won't be good for nebulae even with a filter, as an unmodified camera has a blocking filter before the sensor.

 

So I guess I should try these cameras with my large focal length telescopes, which like larger pixels according to the CCD Calculator.

 

It's too bad because the D750 was giving 6.88 x 4.6 degree images and the D5300 4.5 x 3 degrees with the Askar FRA300.

 

Any suggestions on what combinations or approaches to get the most out of these cameras?  Thanks!

Edited by Sky King, 26 March 2025 - 12:02 PM.

[Sky King]

D750, Askar FRA300 star field around SH2-240, 6.88 x 4.6 degrees.

 

 

[Kevin_A]

I have the askar FRA300 and i can thread a filter into the back end m48 scope adapter ring on the inside of it… then put the t-ring and camera on it. 

[Sky King]

I have the askar FRA300 and i can thread a filter into the back end m48 scope adapter ring on the inside of it… then put the t-ring and camera on it. 

Thanks, I'll try that. Odd it's not better designed for DSLRs.

[Kevin_A]

Thanks, I'll try that. Odd it's not better designed for DSLRs.

I think that they dont think much about dslr users because of the limitations of un modified sensors. So using a dualband filter is pointless and stock filters cut out uvir anyways.

[Sky King]

I have the askar FRA300 and i can thread a filter into the back end m48 scope adapter ring on the inside of it… then put the t-ring and camera on it. 

Yes that worked! Thanks for the tip! As you pointed out, the un modified DSLRs don't work with dualband filters and I don't know if my D5300 Ha modified would benefit either. Guess I'll try it. But I'm getting to like what the Askar FRA300 can do.