Esprit 100ED & ASI385MC cooled for galaxy imaging?

[Icesheet]

I'm never entirely sure which sub-classification to put a post so please move this if necessary!

 

I always dread galaxy season as it's a sure reminder that the light nights are approaching here and I don't really have the equipment to do it justice anyway. It has always been my intention to get something with a longer FL in the future but that would also require a mount upgrade and the funds aren't there yet. Now, by chance I have the opportunity of picking up a used ZWO ASI385mc cooled (I already have the ASI1600mm).

 

I plugged all the details into the astronomy tools site and this small sensor with my Esprit 100 gives me a lovely FOV on many of the galaxies with seemingly ideal sampling of 1.4"/pixel.  I'm the first to admit that I've not got my head completely around, sampling, resolution, pixel size etc so what is the sting in the tail here. Would it be my lack of resolution with the bigger pixels and aperture meaning I'll sacrifice a lot of detail in my images? Or could this turn my Esprit into a feasible dual purpose scope at a fraction of the price?

There wasn't that much on AstroBin and nothing I could find paired with an Esprit so I'm thinking there must be a reason for that! 

 

Advice greatly appreciated

 

 

[Juicy6]

You are using a ASI 1600, right? With a ASI 385 you will have almost same pixel size as in ASI 1600 but on a chip a tenth the size. So essentially you are cropping image when shooting instead of in post processing.

Christer, Sweden

Edited April 22, 2019 by Juicy6

[Icesheet]

You are right! So glad I posted this (dumb) question here. Saved me money buying this camera but will probably end up costing me more on a new scope in the future now 

 

Much appreciated.

Edited April 22, 2019 by Icesheet

[Adam J]

On 22/04/2019 at 11:14, Icesheet said:

You are right! So glad I posted this (dumb) question here. Saved me money buying this camera but will probably end up costing me more on a new scope in the future now 

 

Much appreciated.

yes but with 0.8e read noise at 200 gain its significantly more sensitive so you can do short exposures <10seconds and get more detail. Now would you want to do 10 second exposures with an ASI1600......well no because that would be far too much data.

[Juicy6]

Agree.

Edited April 24, 2019 by Juicy6

[Icesheet]

Aw c’mon guys I’m indecisive as it is haha. 

14 hours ago, Adam J said:

yes but with 0.8e read noise at 200 gain its significantly more sensitive so you can do short exposures <10seconds and get more detail. Now would you want to do 10 second exposures with an ASI1600......well no because that would be far too much data.

Can you explain how I would get more detail? Is it because lots of short exposures would compensate for poor seeing? Almost like ‘lucky imaging’ but for galaxies?

[Adam J]

3 minutes ago, Icesheet said:

Aw c’mon guys I’m indecisive as it is haha. 

Can you explain how I would get more detail? Is it because lots of short exposures would compensate for poor seeing? Almost like ‘lucky imaging’ but for galaxies?

Yes that is exactly how, you need to look up DSO lucky Imaging. Although it is something normally done with mono cameras.

Edited April 24, 2019 by Adam J

[Icesheet]

46 minutes ago, Adam J said:

Yes that is exactly how, you need to look up DSO lucky Imaging. Although it is something normally done with mono cameras.

Thanks! I’ll look it up then. 

[ollypenrice]

1.4"PP will give you quite reasonable scale on lots of galaxies. What your sky will ultimately allow in terms of resolution is something you'll need to find by experiment. I feel that mine will allow about 0.9"PP on good nights.

Olly

[Icesheet]

37 minutes ago, ollypenrice said:

1.4"PP will give you quite reasonable scale on lots of galaxies. What your sky will ultimately allow in terms of resolution is something you'll need to find by experiment. I feel that mine will allow about 0.9"PP on good nights.

Olly

If I did get it I would be hopeful the lucky imaging method Adam mentioned would compensate somewhat for poorer skies. I'm actually half tempted to give it a bash with the ASI1600mm then crop the image.

[Adam J]

2 hours ago, Icesheet said:

If I did get it I would be hopeful the lucky imaging method Adam mentioned would compensate somewhat for poorer skies. I'm actually half tempted to give it a bash with the ASI1600mm then crop the image.

 The minimum number of exposures to do it right is about 2000....how much storage space / time to stack 2000 x 16mp images?

5 seconds or less exposures at very high gain is where you want to be.

I believe something like 64GB of data. The advantage of the smaller camera is that you can actually stack it in less than 48 hours lol.

The other issue is read time, you will lose a significant amount of time reading the data from the camera between exposures.

Edited April 25, 2019 by Adam J

[Icesheet]

31 minutes ago, Adam J said:

 The minimum number of exposures to do it right is about 2000....how much storage space / time to stack 2000 x 16mp images?

5 seconds or less exposures at very high gain is where you want to be.

I believe something like 64GB of data. The advantage of the smaller camera is that you can actually stack it in less than 48 hours lol.

The other issue is read time, you will lose a significant amount of time reading the data from the camera between exposures.

64gb is right (0.032gb per image). Download time per image should be 1-2 sec. My acquisition laptop is fairly high spec and has a 500gb ssd. 

 

Stacking might be the issue but my processing desktop has an 8th gen i7, 32gb RAM and a decent graphics card. Might as well give it a test!

 

 

[Icesheet]

Maybe 4 hrs imaging time for 3 hrs of data? In theory. At least to see if the results are worth investing in a new camera

[Adam J]

13 hours ago, Icesheet said:

Maybe 4 hrs imaging time for 3 hrs of data? In theory. At least to see if the results are worth investing in a new camera

Ok, why not give it a try, although you need to understand that you should not expect get much at all in individual subs at 5 seconds, it requires a bit of faith in the final product.

Also pick something bright like M82 for your first try.

Adam

[vlaiv]

Although I do think highly of ASI385, for this purpose I think you will do better with ASI1600.

Even if you do short exposures and try lucky DSO imaging. ASI385 is very very good planetary camera, and if you want to try that, then by all means - get it.

But in comparison to ASI1600, we are talking significant difference that could, and probably will, offset small read noise difference. OSC vs MONO (I gathered that you have ASI1600 mono cooled).

One thing that people often don't take into account - OSC camera can be viewed as one with twice larger pixel size (for sampling resolution calculations) - that has 1/4 QE in Blue and Red and 1/2 QE in green of mono version but can shoot R, G and B simultaneously

It's a bit of brain twister to see how it compares to mono version in term of performance. I'm in favor of mono being a better choice in many respects.

On a separate note - I think ASI1600 supports ROI, right? You don't need to download and store full frame for each sub - that will lessen load on storage and processing.

[Adam J]

32 minutes ago, vlaiv said:

Although I do think highly of ASI385, for this purpose I think you will do better with ASI1600.

Even if you do short exposures and try lucky DSO imaging. ASI385 is very very good planetary camera, and if you want to try that, then by all means - get it.

But in comparison to ASI1600, we are talking significant difference that could, and probably will, offset small read noise difference. OSC vs MONO (I gathered that you have ASI1600 mono cooled).

One thing that people often don't take into account - OSC camera can be viewed as one with twice larger pixel size (for sampling resolution calculations) - that has 1/4 QE in Blue and Red and 1/2 QE in green of mono version but can shoot R, G and B simultaneously

It's a bit of brain twister to see how it compares to mono version in term of performance. I'm in favor of mono being a better choice in many respects.

On a separate note - I think ASI1600 supports ROI, right? You don't need to download and store full frame for each sub - that will lessen load on storage and processing.

I am not sure that it does support ROI, at least I have never found that option on mine.

Edited April 26, 2019 by Adam J

[vlaiv]

8 minutes ago, Adam J said:

I am not sure that it does support ROI, at least I have never found that option on mine.

This is from ZWO website on ASI1600MM Pro description page:

I'm not sure that ASCOM drivers support ROI, but native ones do. For short exposures and ROI feature I would probably go with SharpCap or similar rather than full fledged capture app like SGP. Native drivers enable very high download rates. My ASI1600 in SGP needs about 1-1.5s per sub download - not sure why ist that because it should be able to deliver at least 14fps over USB3.0 - the way I use it. On 5 second exposures, 1s is 20% time waste - so using native drivers in the app that supports it certainly looks like better option.

[Owmuchonomy]

As said above just use ROI capture. It’s quite possible in Firecapture for longer exposure times. Then you just mimic the smaller chip size without buying another camera. I agree, a mono option will give you better results overall.

[Icesheet]

There are not many nights left for me to try at 60degN but if I can get out I will give this a bash. Thanks for the input. Learned a lot from this and likely saved myself some pennies! 

[wimvb]

Emil Kraaikamp did a lot of lucky imaging with a small sensor and a large/fast dob. Have a look at his site

https://www.astrokraai.nl

He is the developer of the software autostakkert!.

With a colour camera you should have a pixelscale slightly worse than the theoretical p*206/fl, because of debayer interpolation.

[gorann]

You say your current mount could not handle a bigger scope with longer FL. What mount do you have? An EdgeHD8 weighs exactly the same as your Esprit 100.

Edited April 27, 2019 by gorann

[Icesheet]

2 hours ago, wimvb said:

Emil Kraaikamp did a lot of lucky imaging with a small sensor and a large/fast dob. Have a look at his site

https://www.astrokraai.nl

He is the developer of the software autostakkert!.

With a colour camera you should have a pixelscale slightly worse than the theoretical p*206/fl, because of debayer interpolation.

Wow some of those ISS images are amazing! Thanks, I was actually aware of that software so I’ll look into it again. 

[Icesheet]

52 minutes ago, gorann said:

You say your current mount could not handle a bigger scope with longer FL. What mount do you have? An EdgeHD8 weighs exactly the same as your Esprit 100.

Currently I’m using a belt modded HEQ5.

Funny you should mention the EDGE 8 as there was a used one on FINN.no recently and I seriously considered buying it. It wasn’t really just the weight but how well the HEQ5 could handle that FL. Probably already pushing it with the Esprit. 

Anyway I’ve now decided I’ll upgrade my mount instead. Hopefully later this year if funds allow. I’m swaying between the EQ6-R and the CEM60. My head says the CEM60 but my pocket says EQ6- R

Edited April 27, 2019 by Icesheet

[wimvb]

59 minutes ago, Icesheet said:

I’m swaying between the EQ6-R and the CEM60

At your location, you have to consider the range and method for latitude settings. That's what made me choose the AZ-EQ6 above any other sw mount. 

Edited April 27, 2019 by wimvb

[Icesheet]

What are the advantages @wimvb? I do get frustrated with the adjustment bolts on the HEQ5 but are these not upgraded on all new SW models now? Am I missing something?