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Imaging very small targets

astrophotography imaging reflector
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#1 Karlp295

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Posted 04 December 2020 - 02:31 PM

I am imaging a number of targets these days and have a question about how to best capture details of small objects such as the Ring nebula or the Blue Snowball nebula etc.

 

I imaged as normal with my 130mm SLT Reflector on an AZ ALT mount. I can manage at most 60 seconds in the west and east.

When zooming these objects after stacking the details are very poor. Should I use the projection method with the eyepeice in the tube attached to my DSLR because I normally image at prime focus and was not very happy with the reselts on these small objects.

 

Has anyone experience of imaging such objects with a reflector?

 

 

 

 

 



#2 Huangdi

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Posted 04 December 2020 - 03:01 PM

I am imaging a number of targets these days and have a question about how to best capture details of small objects such as the Ring nebula or the Blue Snowball nebula etc.

I imaged as normal with my 130mm SLT Reflector on an AZ ALT mount. I can manage at most 60 seconds in the west and east.
When zooming these objects after stacking the details are very poor. Should I use the projection method with the eyepeice in the tube attached to my DSLR because I normally image at prime focus and was not very happy with the reselts on these small objects.

Has anyone experience of imaging such objects with a reflector?


Ab Aps-c or even worse full frame dslr simply isn't suited for such small targets. A common technique is using a high speed cmos camera and capturing the bright parts of those nebulae with 1 second, or sometimes even sub-second exposures.

Dslr's are wide field instruments..

#3 bobzeq25

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Posted 04 December 2020 - 03:01 PM

Three big things to know.

 

Tracking is key to imaging small targets.  So, imaging small targets on an alt-az mounts is just not going to work.

 

Related.  Imaging small targets needs a scope with a long focal length.  Long focal lengths require better (ie expensive) equatorial mounts.

 

Imaging small targets is difficult for someone relatively new to this.

 

Bottom line.  What you have can work some for DSO astrophotography.  But not on small targets.  There is no magic solution to fix that.  The real solutions require substantial sums of money, substantial experience.

 

Minor point.  Eyepiece projection can work with very bright planets.   They're so bright, the reduction in brightness is not a big deal.  With DSOs, which are very dim, the reduction in brightness ruins the image.  Again, no magic solution for the problem.  DSO imagers don't use eyepiece projection, it's a solar system technique, only.


Edited by bobzeq25, 04 December 2020 - 03:02 PM.

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#4 17.5Dob

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Posted 04 December 2020 - 03:03 PM

You need a lot more native focal length as well as aperture. Adding a barlow or using eyepiece projection is going to slow your existing system down too much.

But a lot of planetary nebula are pretty bright, it "might" be possible.to do a "little" better....



#5 bjulihn

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Posted 04 December 2020 - 03:15 PM

You are clearly pretty dedicated to be attempting these targets with an alt-az mount. I believe your skill level has caught up to your equipment's capability. You are no longer the limiting factor. It is time to consider a decent equatorial mount. The starting price for a mount capable of what you want to do is around a $1,000 and up. Though you might find a used one a little cheaper.

 

Most of us who are budget conscious have tried desperately to find a cheaper solution only to get frustrated with poor tracking or other issues and either quit or sell that cheaper solution and bite the bullet on something that actually works. I wish you well in this adventure. 


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#6 Sky King

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Posted 04 December 2020 - 05:41 PM

These folks have given you good advice. But there may be another direction to consider: EAA.  Electronically Assisted Astronomy  is more forgiving than AP. In this video he is using   

 

Scope: TPO 6" f/4 Imaging Newtonian

Camera: ZWO ASI178MC
Mount: Celestron Evolution AltAz on homemade tripod
Planetarium Software: Stellarium
EAA Stacking Software: SharpCap Pro 3.2

 

Good for light polluted areas, and a lot of fun. You could get a ASI224MC or something similar, an old laptop and Sharpcap Pro is $15 a year. This doesn't mean you can't get a good mount and do AP with guiding later on. It's just a fun alternative to consider. 

 

Stack 6frames 91s WithDisplayStretch

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#7 StarryHill

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Posted 04 December 2020 - 05:45 PM

Imaging small, dim targets is challenging. One of the most important factors  is your 'seeing' conditions -- how stable your skies are. You can have a high-end, very expensive setup and still not get fine details if your conditions aren't great. On most nights in my area, conditions aren't great.

 

For nights when your skies are stable, you'll need a mount that tracks well... for most of us, this means an equatorial mount with a guiding scope/camera setup. You can enter this market for about $1k but many of the better photos you see of small targets were taken with mounts costing much more.

 

Also, there's only so much detail you'll be able to capture with your 130 SLT even with a better mount. A larger, higher quality telescope will be capable of greater resolution (detail) with small, dim targets. So, if you are thinking about getting a different mount, you might want to consider one capable of carrying a heavier future telescope.  


Edited by StarryHill, 04 December 2020 - 05:46 PM.

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#8 Karlp295

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Posted 05 December 2020 - 04:31 AM

Thanks for all this valuable advice confirming what I really already know, I need to spend some money on an EQ mount etc. Problem is I am in Turkey with great clear skies and limited access to equipment as I need to order from abroad which adds considerably to the cost. After Covid ends I will go to the Uk to pick up something but until then I either pay a very high price or stick with what I have.



#9 bobzeq25

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Posted 05 December 2020 - 12:15 PM

Thanks for all this valuable advice confirming what I really already know, I need to spend some money on an EQ mount etc. Problem is I am in Turkey with great clear skies and limited access to equipment as I need to order from abroad which adds considerably to the cost. After Covid ends I will go to the Uk to pick up something but until then I either pay a very high price or stick with what I have.

The good things.  There are a large number of big bright targets suitable for your budget.


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