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Old 09-05-2020, 08:03 PM
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Outcast (Carlton)
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Imaging with a powermate...

So...

Current setup is a Canon EOS70d & either an 80mm f6 triplet or a 130mm f5 Newt mounted on an AZEQ6 & about to embark upon guiding using a ZWO ASI224MC & 60mm guidescope controlled through Stellarmate.

I've been looking at various targets that I might like to have a crack at & M83 has grabbed my attention.. however, at prime focus in either of these setups, it's not gonna be a particularly large object...

So... I got to thinking... what if I add a powermate... I currently own a 1.25" 2.5x powermate... hmmm, then I thought... I can't use my coma corrector with that on the newt (size) or, for that matter my field flattener on the Refractor (size again)...

So, then I did some googling & stumbled across an old thread asking similar questions by Stonius... got a partial answer.. seems I might not need the flattener if I introduce a powermate...

What about a Coma corrector on the Newt?

I understand that introducing either a barlow or powermate also changes the FL of my scope by the factor of the barlow.. ie: 2x barlow would render the 80mm at f12 & the 130mm Newt at f10...

So, 2nd question... if I introduce a powermate should I go with 2x or 4x... &, what problems am I potentially setting myself up for here that I haven't thought about?

Thanks in advance...

PS: Ryan... if you are reading this, I'm just asking.... LOL...
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Old 09-05-2020, 08:23 PM
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Outcast (Carlton)
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Or conversely,

Would I perhaps be better chasing small objects such as galaxies with my 7" Mak at a native f15?
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Old 09-05-2020, 08:54 PM
Startrek (Martin)
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Carlton
My image scale and FOV on my 6” f6 and 8”f5 are great for most objects but I did experiment with my Powermates ( my 2 x and 2.5x ) a year or so ago and even though you increase the size of the image in the frame you certainly sacrifice a great deal of resolution. So I came to the conclusion that they are primarily designed for planetary imaging which is what I use them for now. My 5 x Powermate is perfect for both my newts in particular Saturn and Jupiter whereas I use the full set when imaging the moon ( both wide field and lunar terrain images )
Can you upgrade your 130mm newt to a 6” f6 newt ( focal length 900mm ) Mine can image galaxies like M83 , Sombrero , Centaurus A etc... without a problem using my Canon 600D APS-C crop sensor and the object size in the frame is adequate ( you’ve see some of my posted images of these objects ) Not quite sure what your sensor size is on the 70 D ?

Cheers
Martin
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Old 09-05-2020, 09:07 PM
raymo
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Your 7" Mak is the ideal scope for imaging planetary nebulae, and many of them are very distinctive. NGC 3918 is a good place to start,[and being bright, it is easy to find] it takes high magnification well. Years ago I did some eyepiece projection imaging of it with my 8" Newt. It is a fascinating object. M57 is another really good one.
raymo
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Old 09-05-2020, 09:07 PM
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Outcast (Carlton)
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Hey Martin..

EOS70d is an APS-C same size as yours...

I could upgrade to a 6" but, I don't really want to.. The Vixen is an absolute corker of a scope that I picked up from Ryan for a bargain...

I haven't done a lot of imaging with it yet but, what I have done looks great & that's without guiding

Plus, as a grab & go visual scope it is utterly stunning.. I kid you not...

Had it on the moon one night with a 2.5mm Vixen SLV EP & the views of Copernicus were simply stunning.. so crisp..

Not withstanding, if I keep the Vixen then, I've nowhere to put a 6"... my wife will take more body parts... and there isn't much more to give...

There is no way I'm letting that Vixen go though... it's an absolute gem
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Old 09-05-2020, 09:16 PM
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Quote:
Originally Posted by raymo View Post
Your 7" Mak is the ideal scope for imaging planetary nebulae, and many of them are very distinctive. NGC 3918 is a good place to start,[and being bright, it is easy to find] it takes high magnification well. Years ago I did some eyepiece projection imaging of it with my 8" Newt. It is a fascinating object. M57 is another really good one.
raymo
Thanks Raymo, good to know...

How do you think it would go on galaxies such as M83 & the like...

The image scale looks better than say with my 80mm or 5" newt but, I have no idea about imaging galaxies & how it might or might not shape up in a long focal length Mak..

I understand that imaging will require longer exposures Vs my much faster refractor or Newt..

Cheers
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Old 09-05-2020, 09:18 PM
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Outcast (Carlton)
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Quote:
Originally Posted by Startrek View Post
Can you upgrade your 130mm newt to a 6” f6 newt ( focal length 900mm )

Cheers
Martin
Damn you Martin.. now you've got me looking at the price & my shelving to see where one might fit....

My life will be in mortal danger!!
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Old 09-05-2020, 09:48 PM
Startrek (Martin)
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Bintel have their 6” f6 newt for only $399
Although I think that’s with a single speed focuser ( photo shows single speed )
When I bought my Bintel 6” f6 newt 3 years ago it was upgraded with a dual speed focuser at no cost.I originally bought it for visual ( great visual scope too !!! ) as at the time I hadn’t considered to do any serious imaging but when I borrowed my wife’s old Canon and starting snapping 20 and 30 second images standing next to the mount using a remote shutter release , I caught hook line and sinker into AP. 6 months later came guiding and pushing 5 minute subs on galaxies, nebs and clusters
Alex ( Tabulam ) always said the 6” newt is great scope for AP and he’s not wrong
The only mod I’ve done on mine is fit better primary mirror springs 6 months ago as collimation was drifting a bit
It’s a real workhorse and great all rounder for DSO and planetary imaging

Martin
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Old 09-05-2020, 09:51 PM
raymo
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On the brighter galaxies such as NGC 253, and M83, it will do well, but on fainter ones you would need to up the ISO in order to keep your sub lengths
acceptable. I haven't followed your progress closely, but if you have mastered
long exposure guiding, you can work wonders with that scope.
Just saw Martin's post, 900mm is not enough focal length if you want to get seriously
into galaxies, unless you are prepared to stick with only the largest ones. Many quite
bright ones are too small even with my 1000mm f/l. 900 is also virtually useless for planetaries.
The simple answer is that no one scope fits all.
raymo

I have added a pic of NGC 3918 taken with 1,000mm + 2x Barlow =2,00mm and enlarged to about 10,000mm.
Attached Thumbnails
Click for full-size image (3918-+-barlow-019-down.gif)
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Last edited by raymo; 09-05-2020 at 10:18 PM. Reason: more text and add image
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Old 10-05-2020, 09:48 AM
Startrek (Martin)
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Raymo
Couldn’t agree more about focal length and galaxy imaging, especially the dim ones
In regards to galaxies I like to push my 6” to the limits with good collimation, tight focus , clean optics , hours and hours of 5 minute subs , dithering, darks , stacking and good processing using Startools.

Carlton
Attached image of NGC 6744 Pavo galaxy a 9.2 magnitude object ( not exactly a bright object ) taken with my 6”

Cheers
Attached Thumbnails
Click for full-size image (7AF03946-4B6B-4821-A955-AF3DDA565509.jpg)
160.3 KB90 views
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