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Mosaic w/ED127 or shorter FL?

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#1 ssa2294

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Posted 16 October 2020 - 08:44 PM

Take M31 or Orion as examples of targets. For the example I can use an ED127 w/952 focal length, but to capture fully I would need to make a 3x3 or 4x4 mosaic and combine in PI.

 

Alternative would be to use a shorter focal length to capture fully the object.

 

If my objective was to get the fullest detail, I am interested to know and understand why I would not use the ED127 and mosaic the image (knowing this would require 9-12x the length of time to capture is irrelevant for this scenario). Camera could be Nikon APS-C, ZWO ASI2600MC or 2600MM LRGB if that factors in any.



#2 SilverLitz

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Posted 16 October 2020 - 11:23 PM

M31 is huge and needs MUCH less FL, even on APS-C it would be best w/ ~350mm FL.



#3 Stelios

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Posted 17 October 2020 - 02:16 AM

In addition to capture, figure extra time for processing the mosaic. To most people the time difference *would* be relevant. But if  you want to capture the maximum possible detail, say for a 24"x30" print, go for it. 

 

Do realize that an issue you may have as well is changing conditions. You may be unable to match seeing quality (stars, detail) across all frames of the mosaic, although if you shoot all panels each night this would be alleviated in part. If you get a mono camera for this you better have parfocal filters--you don't want to be refocusing on filter changes, 

 

A concern would also be image scale vs. seeing. For the ASI2600 for example, your scale is 0.8. If the seeing at your location is poor, you may be oversampled and not able to benefit from the theoretical resolution.



#4 ssa2294

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Posted 17 October 2020 - 08:23 AM

I don't have any concern about extra processing time, I have already factored that in when deciding to add a mono (whenever 2600MM is released) after using DSLR. Sad reality is I have more processing time than actual shooting time (don't we all?). 

 

This question came up when I took a look at NINA and it's features, I came across Framing. It was there I saw that I could create mosaic, set overlap %, then add this as a sequence and save it to return multiple nights. 



#5 endlessky

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Posted 18 October 2020 - 02:50 AM

Sad reality is I have more processing time than actual shooting time (don't we all?).

Unfortunately, this is true for me as well. And it's the first thing I thought about when I read your first post.

 

If shooting time is an issue, because clear nights are more of a rarity than the rule, doing mosaics is going to be even harder. I find it quite hard as it is to reach my target amount of hours, during multiple nights, on the same subject, when I can image all of it at the same time because it fits with my focal length/camera combination. If I had to do a mosaic, it would literally take months.

 

True, the mosaic might give you more details (if seeing conditions allow), but it's also true you can basically double your final resolution by drizzle (or Bayer drizzle) integration.




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