iannz
Member
Posts: 71
home town/country: Tarurutangi, NZ
time zone gmt +/-: +12
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Post by iannz on May 22, 2020 5:16:24 GMT
so I thought I better put up something mildly astro related besides crashing everyone's threads.....
Last nite, no (hardly) any wind and with a high thats been here for a week or two (driving the farmers crazy, no rain wtf? in NZ?) and quite dry for this time also. So I drag the CGEM-DX I aquired recently, new to me, and after commentary from Paul thought I should check it and Polar alignment (Sharpcap) out ...... Well, went waay easier than anticipated, generally less than 20" (I think thats right) and more like 18-15" variation on both axes. Got an excellent from SC anyway so good 'nuff. The really enticing thing about all this is being able to pick something out of the mount's database and having it whip round and on it. Close enough anyway, about a finger width away from center (if that means anything). Also found I can't track any more than maybe 30 seconds before elongating the stars. Damn. Haven't quite explored that part yet. Mount level etc too. Also that I can't see anything at the Raw 16 setting for the camera (QHY-163c) although Raw8 works fine as well as the RGB24 that the following were done with. Played about with the histo's settings but still having noisy images, more than desired. Haven't got my head around Darks, Flats etc but suppose that will help some too.
A few from the deep south where you northern lot can't see? cheers ian
QHY-163c SCT8se w/6.3 thingy generally -15, 8sec xpos, gain 112, offset 80
C61
C71
C95
C105
C107
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Deleted
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Post by Deleted on May 22, 2020 10:53:32 GMT
Gidday Ian I havent got my head around darks and flats either. I always try to keep exposures under 30 secs if I can, but that requires fast scopes with sensitive cameras. I notice all your posted images are under 10 sec exposures and all the stars are nice and pinpoint Your QHY 163 is a big sensor and with your setup 6.3 focal reduction is about as low as you can go without vignetting and coma. That will mean you will probably have to persist with 30 sec exposures for dim dso's. Not such a problem for the brighter nebulae. I have a similar problem with my ZWO 294 on my 8' sct. Its sensor is too big for the night owl 0.4 fr so I need to do longer exposures at 6.3fr. cheers Paul
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Post by Dragon Man on May 22, 2020 11:49:14 GMT
Ian, all your images look good mate. Stars look nice and sharp. I must admit though, it is strange seeing them with their Caldwell Catalogue names instead of their NGC names
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iannz
Member
Posts: 71
home town/country: Tarurutangi, NZ
time zone gmt +/-: +12
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Post by iannz on May 22, 2020 20:32:30 GMT
hi guys and thanks for the comments. Ken - I never thought about the objects even being in or labeled under other catalogues, just went for the item (closest) in the Caldwell database on the controller. Interesting point, does the site have a preference for labeling items? Paul - thanks for the thoughts. A bit counter intuitive for me tho, I was thinking the focal reduction would ensure a better coverage although since its not physical is the point? I think of it as a wide/r angle lens on the camera? ta ian edit: Ok, went to "ccd tools" and had a play and see what you mean. another nudge to the Hyperstar......
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Deleted
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Post by Deleted on May 23, 2020 12:16:27 GMT
Gidday Ian Are you referring to all that oversampling , undersampling stuff? I am not sure what to make of all that for VA. For me, the most important consideration is FOV. For instance if you bought a hyperstar for your 8" sct, then the FL would be 400. For nebulae the FOV would be pretty well spot on, but if you were imaging small galaxies such as the Leo Triplet the FOV is too big and the galaxies too small. If you changed cameras to a ZWO 224 which has about the same pixel size as your camera but the sensor size is about 1/3, then the FOV is about a 1/3 as well and the galaxy image is much bigger. The ccd tools will tell you the resolution and sampling is just right for both cameras. For me, the FOV is the important figure.
cheers Paul
edit. I find f6.3 on the sct is just a tad slow and hence the need for longer exposures for the dim dso's.
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Post by Dragon Man on May 23, 2020 13:04:58 GMT
hi guys and thanks for the comments. Ken - I never thought about the objects even being in or labeled under other catalogues, just went for the item (closest) in the Caldwell database on the controller. Interesting point, does the site have a preference for labeling items?
Nah, use any catalogue you want. I usually know objects by their common name, not by a catalogue number anyway Like in your first pic, labelled C61 (C60/61). Also known as NGC4038 and NGC4039, but I just call them the Ringtail Galaxies. Americans like to call them the Antennae Galaxies. Some people simply refer to them as the Colliding Galaxies in Corvus Use any name or catalogue you prefer
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iannz
Member
Posts: 71
home town/country: Tarurutangi, NZ
time zone gmt +/-: +12
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Post by iannz on May 23, 2020 23:36:13 GMT
Ok Ken, you're ahead of me there. Be a while before I'm up with the myriad of labels that get used. Just another option that came up for selection in the bit of sky I was pointed at. Frankly, it looks more like a tadpole to me..... Paul; thanks for the comments/thoughts. Wasn't aware of considering the different cameras that way. Oh, and thanks for nothing..... you've given me a valid reason to buy more Astro toys. lol. At this point I want to get on top of the tracking a bit more as a goal plus the camera re less noisy images. Of course there's the additional post processing fiddling too. Plenty for retirement ! cheers guys
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