2 replies to this topic

[sky_lounge]

Looking to get into some light lunar AP with an untracked/manual 8" Dob (200/1200)

 

I've been looking at the planetary "rules of AP" but having a hard time selecting between the ZWO ASI585MC and the ZWO ASI676MC

 

I guess according to the "rules" of 5x pixel size = target f/ratio, either it's f/14.5 with the ASI585 and f/10 wit the ASI676.

 

Since I own a 2x Barlow already I included that calculation; putting me at f/12, which is right in between the two.  

 

 

Since I'm untracked I'm assuming FOV and FPS is paramount (FOV is comparable between the two). 

 

I'm in suburban skies and occasionally travel a bit to rural, so almost never have excellent seeing. So if one is better assuming not excellent seeing that also is relevant.

 

For Lunar AP, is it better to be a little "over" the "5x Pixel Size" or "under" it?

 

FOV is comparable between the two, so I'm not as concerned about that, more about getting the best detail.

 

Is there a target Pixel Scale I should be looking for?

 

Just based on Pixel Scale I would be thinking the 676 is better, but a lot of people here seem to prefer the slightly larger pixels of the 585.

 

(Also, if it's there's a big difference in ability to do some light untracked EAA on smallish objects where FOV doesn't matter, such as globs e.g. M13, that would also influence my decision i.e. would be willing to give up a bit of detail if 585 has a non-negligible difference to do light EAA)

 

 I know an EQ mount + tracking is really the way to go for best results with AP, but just curious what's possible here.  If the answer is that it's really not possible with an EQ mount, that's OK too.

Edited by sky_lounge, 11 June 2025 - 11:06 PM.

[Borodog]

You can image the Moon with an untracted Dob. But I would recommend investigating an equatorial platform. If you are handy there are plans online that can be built for under $100.

If you really want to try untacked imaging, I would skip the Barlow. The Moon is going to move FAST. It moves at about 15”/s, or its own diameter every 2 minutes. Use astronomy.tools to figure out the FOV of a scope + camera combo, and then visualize how fast the Moon moves through the FOV by visualizing the disk moving over one radius; that’s how far it will move in one minute.

You CAN make critically sampled imaged untracked with a relatively large aperture, but it’s hard and takes special processing. I keep threatening to make a video demonstrating the technique, but we’re in the rainy season and I still have not had the chance.

[Borodog]

Oh and the correct camera is the 676.