Advice needed

[PatrickO]

Hi All

I want to do some detailed images of the lunar surface. Such as individual large craters and mountain ranges. Planning to use video "lucky imaging".

I have a Celestron Nexstar 4se 100mm Mak. For cameras I have a ZWO ASI224MC and also a Nikon crop sensor D7200.

To get the FOV I want I can use a Barlow with the Nikon or a reducer with the ZWO.

I already have a good quality Barlow, but would have to buy a reducer.

Advice on the best options and technique much appreciated.

[Swoop1]

Patrick,

Have you used the Field Of View Calculator on Astronomy Tools to get an idea of what your combinations will achieve with varous barlows/ reducers?

It gives a good idea of what results you may get thriugh your set up

https://astronomy.tools/calculators/field_of_view/

 

[Yawning Angel]

Personally, with those options I'd go for the asi224 without a reducer or barlow, and assemble a 2 x 2 mosaic of any given feature. Its pretty simple using Microsoft ICE (free) to assemble the mosaic, or you can have Photoshop do it...or you can even do it manually

If you want to spend money, look at a camera with smaller pixels, to bring you closer to ideal sampling. 2.9nm maybe, from an asi290 / 662 / 664 or 585, depending on budget.

[PatrickO]

18 minutes ago, Swoop1 said:

Patrick,

Have you used the Field Of View Calculator on Astronomy Tools to get an idea of what your combinations will achieve with varous barlows/ reducers?

It gives a good idea of what results you may get thriugh your set up

https://astronomy.tools/calculators/field_of_view/

 

Yes. I've used it to work out what I want. Thanks.

[PatrickO]

5 minutes ago, Yawning Angel said:

Personally, with those options I'd go for the asi224 without a reducer or barlow, and assemble a 2 x 2 mosaic of any given feature. Its pretty simple using Microsoft ICE (free) to assemble the mosaic, or you can have Photoshop do it...or you can even do it manually

If you want to spend money, look at a camera with smaller pixels, to bring you closer to ideal sampling. 2.9nm maybe, from an asi290 / 662 / 664 or 585, depending on budget.

Thanks. Why is using a Barlow or reducer a worse option?

[Yawning Angel]

7 minutes ago, PatrickO said:

Thanks. Why is using a Barlow or reducer a worse option?

The Nikon will produce compressed video...which you can use, but wont be the quality of the ASI, so the Barlow isn't needed.

The beermat maths for sampling is an F ratio around 5x the pixel size. The 4SE is f/13, so you need to aim for 2.6nm ish. If you reduce it, the pixel size naturally shrinks too taking you further from ideal (your 224 has 3.75nm pixels). Of course, seeing plays a huge part, so these differences are less noticeable

You could go for a asi178, which is 2.4nm too, but your 'best' option for FOV without glass (I'd avoid adding glass if it's not needed) would be an asi585 (or equiv from other manufacturers). The trade-off comes in framerate. The bigger the sensor, the slower they can readout. The 224 is blazing fast, and very easy to get along with