To get started with imaging planets (with SW 150PDS)

[Chipela]

What would be the most practical way to extend my visual-only rig (EQ5 + SW 150PDS) to do specifically planetary imaging:

* attach my Canon EOS 100D
* get a web camera
* get a color CCD camera or something similar

As far as I have understood correctly, I'd need a coma corrector, barlow lens and adapters in all options.

What is the practical focal length for planets? Is it impractical to try to reach those numbers with a relatively short OTA (f = 750mm).

Thanks a lot!

 

[Cornelius Varley]

If your camera has a 640x480 cropped video mode then you can start with that. The best device to use would be a dedicated lunar/planetary camera such as a QHY5 or ASI AS120. You will need a barlow lens (probably 4x / 5x) to get a good image scale but you won't need a coma corrector, you will only be imaging from the centre of the field of view so coma won't be a problem.

[iwols]

Quote

 

could you fit the barlow and camera  to an ed80 same

[PeterCPC]

Yes you can but it will give a small image scale.

Peter

[iwols]

9 minutes ago, PeterCPC said:

Yes you can but it will give a small image scale.

Peter

thanks would it be worthwhile or is anther scope the answer for planets

[PeterCPC]

For planetary imaging you want a long focal length scope - something like a C9.25. This is what you would get with the ED80 and a 3X barlow lens and ASI120MC

so it just depends if that would be acceptable to you.

Peter

[iwols]

thanks for that peter and with a c9.25 what would i expect

[PeterCPC]

Something like this

Peter

[PeterCPC]

Here's one of mine taken with the C9.25

Peter

[iwols]

thats nice,is that cropped much

[PeterCPC]

No it wasn't - I seem to have lost the details but I know it was with the ASI120MC and a 2X Barlow. If you compare it with the image generated by Astrotools you can see that it's been cropped a bit.

Peter

[Chipela]

On ‎3‎.‎3‎.‎2016 at 17:08, Cornelius Varley said:

If your camera has a 640x480 cropped video mode then you can start with that. The best device to use would be a dedicated lunar/planetary camera such as a QHY5 or ASI AS120. You will need a barlow lens (probably 4x / 5x) to get a good image scale but you won't need a coma corrector, you will only be imaging from the centre of the field of view so coma won't be a problem.

Thanks for a very clear answer. I did some math to find out the size of Jupiter in pixels when selecting the Barlow so that the sampling is optimal for the resolution of my scope.

--

CN has a formula for optimal focal length: FL(mm) = 3.6 x Pixel Size (microns) x Scope diameter (mm)

For 6" tube and suggested cameras (3,75um pixel size) the formula gives 2025 mm. A suitable barlow would thus be 3x (3x*750mm = 2250mm).

The vertical FoV would be (considering that the height of the 1/3" sensor is 3.6mm): FoV = 2 * atan (sensor size / FL / 2) = 5.5'

Considering the size of Jupiter just now (44.5") that would mean that the diameter of the disc of Jupiter on the image would be: 960 pixels / 5.5' * 44.5" = 130 pixels

Just makes me wonder if this is too small size to be appreciated (assuming that each pixel has information, i.e. capturing conditions and processing are perfect).

[iwols]

hi chipela its confusing knowing what to go for

[Tyson M]

A 6 inch should give you a decent picture with a barlow and web cam. Here is mine with a 4 inch frac

[happy-kat]

A £5 xbox webcam with a nose piece from astrooboot £4 (or make a nose cone from an old 35mm film canister for free ) will let you have a try, start with something then see where you want to go and how much more money you want to spend.