#401  
Old 26-06-2016, 11:07 AM
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codemonkey (Lee)
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Well, here it is. About 1.5hrs worth of 15s subs, many of them not good. Crazy NR applied to the RGB, moderate to the L. Obviously needs way longer subs! Was actually capturing for 3hrs, but the overhead of downloading/analysing the subs ate into the overall time significantly, and I did discard some.
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  #402  
Old 26-06-2016, 12:31 PM
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Looks pretty interesting for 15s subs

The upside of longer subs is less downloading time.
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  #403  
Old 26-06-2016, 01:50 PM
glend (Glen)
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Ok here is my long sub narrowband version of NGC 6188. This was shot over a couple of weeks, just finished up last night. The last time on this target I used 60" subs and despite alot of them I was scraping data off the noise floor to build an image. While the camera is great at 60" for RGB, for narrowband it really does need around 300 seconds. I think this time it is a significant improvement and better reflects the camera's capability. There were over five hours of 300" subs that went into this image, Ha, OIII, and SII in Hubble Pallet scheme.
Shot with the ASi1600 at -25C, and captured with SGP. Stacked in DSS with Darks and Bias frames but no flats.
Processed in Photoshop CC, and I added a synthetic luminosity layer built of the combined Ha and Oiii greyscale data. It could probably use more adjustment but I will return to that another time. I might mention that the combined layers file when saved in Photoshop CC was 1GB! I am still learning Photoshop so I know it can be better.

I have attached a little down quality thumbnail teaser below, for the real deal you will need to follow the Astrobin links here below. The master file copy in Tiff looks better, but Astrobin only takes jpgs, sorry - too bad there is no where to publish it.

Astrobin large: http://www.astrobin.com/full/253314/0/

Details page with histogram: http://www.astrobin.com/full/253314/0/

Comments welcome, and if you look in my Astrobin Gallery you can see the previous 60" sub image right next to it, it's worth checking out the histograms and comparing.
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  #404  
Old 26-06-2016, 02:24 PM
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Atmos (Colin)
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I prefer the orientation of the first but the newer one is certainly a lot cleaner, 300s subs do make a big difference so as to not drag off the noise floor
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  #405  
Old 26-06-2016, 03:07 PM
glend (Glen)
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Quote:
Originally Posted by Atmos View Post
I prefer the orientation of the first but the newer one is certainly a lot cleaner, 300s subs do make a big difference so as to not drag off the noise floor
There is probably a lot more there that i haven't pulled out. Re the orientation the camera was in exactly the same position on the scope, but in the first one i rotated it in processing and cropped to give the 'traditional' view. The orientation allows more detail above and below the 'cloud wall', that is lost in rotation so that the 'cloud wall' runs along the long side of the sensor, imho.
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Old 26-06-2016, 04:20 PM
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Looks pretty good Glen, as the IIS thumbnail hides your tracking error

Besides that, you've got to be pretty happy with the results
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  #407  
Old 02-07-2016, 07:56 AM
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Got my adapter! But I can't reach focus with the guide camera & the imaging camera at the same time (guide cam needs to be closer than the OAG can get it, can't increase distance between the OAG and camera because of flattener spacing). Marvellous. Would have worked if I hadn't tried to get cheeky and save myself an extra adapter... now I'll have to buy the original two I'd planned and have a > $200 paperweight.

Last edited by codemonkey; 02-07-2016 at 08:07 AM.
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  #408  
Old 02-07-2016, 09:37 AM
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That is real bad luck Lee, its a money pit this hobby.

Bill
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  #409  
Old 02-07-2016, 10:27 AM
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That does suck Lee, maybe someone on the IIS Classifieds will want your adapter?
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  #410  
Old 02-07-2016, 10:31 AM
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is there any way to get a small positive lens inside the guide adapter to act as transfer lens. If you can do it, you could refocus the guider beam further out. I bluetacked in a positive correcting lens from an otherwise useless Barlow when I was messing around with an OAG, but I guess you could find something useful in any old eyepiece - you need a short focal length lens and will have to experiment with placement, but it does work.

the alternative would be to put a negative lens (essentially a Barlow) closer than the guider focal plane and throw the focal plane out further. The disadvantage of this is that the guide image will be larger and dimmer, which will make it more difficult to find a star - might be OK with binning though. Again, a suitable lens should be available in an old eyepiece or you could try an actual short 2x Barlow if you can get it down deep enough in the adapter

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Old 02-07-2016, 10:44 AM
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Wow that's gotta suck Lee! Hopefully you can sort something out. This hobby is expensive enough without these kind of dramas.
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  #412  
Old 02-07-2016, 11:26 AM
glend (Glen)
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Pointing out the obvious, with a separate guidescope you would not have this problem. At a focal length of just 840mm your not likely to have to worry about differential flex.
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  #413  
Old 03-07-2016, 11:31 AM
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Thanks Bill, Colin and Rex. It's really my own fault for trying to cheap my way out of it in the first place. Changed my order at the last second and didn't put enough thought into it.

Quote:
Originally Posted by Shiraz View Post
is there any way to get a small positive lens inside the guide adapter to act as transfer lens. If you can do it, you could refocus the guider beam further out. I bluetacked in a positive correcting lens from an otherwise useless Barlow when I was messing around with an OAG, but I guess you could find something useful in any old eyepiece - you need a short focal length lens and will have to experiment with placement, but it does work.

the alternative would be to put a negative lens (essentially a Barlow) closer than the guider focal plane and throw the focal plane out further. The disadvantage of this is that the guide image will be larger and dimmer, which will make it more difficult to find a star - might be OK with binning though. Again, a suitable lens should be available in an old eyepiece or you could try an actual short 2x Barlow if you can get it down deep enough in the adapter

rough drawing attached
Ray, that's genius! The OAG has a helical focuser which leaves a bit of space, definitely enough for a small lens.

I dismantled the eyepiece (28mm) that came with the Esprit last night and tried to use the front element to do this.

I tried racking the focuser in and out but couldn't see any stars though I knew they were in the FOV. I didn't try very long as I just wanted to get some imaging done for once and decided to temporarily do away with the flattener.

I'll give this more of a trial though, might be that I just needed more distance between the lens and the guide cam.

Quote:
Originally Posted by glend View Post
Pointing out the obvious, with a separate guidescope you would not have this problem. At a focal length of just 840mm your not likely to have to worry about differential flex.
Cheers Glen. It's more about your imaging resolution than the focal length. I started with an OAG, went briefly to a guidescope, and even when sampling at lower resolution (higher "/px) I could see flex issues. I'm back to an OAG now (obviously) and I don't see myself ever looking at a guidescope again.
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Old 03-07-2016, 11:55 AM
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Actually, having re-read your post, Ray, I'm guessing that 28mm eyepiece is too long. Any suggestions on what focal length might work? Would a 4mm plossl do the trick?

I'm considering buying a cheap, short focal length eyepiece, as if I can make that work, it'll save me hundreds.

I don't know anything about eyepieces, as I started out doing astrophotography and have never done visual.
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Old 03-07-2016, 12:56 PM
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Quote:
Originally Posted by codemonkey View Post
Actually, having re-read your post, Ray, I'm guessing that 28mm eyepiece is too long. Any suggestions on what focal length might work? Would a 4mm plossl do the trick?

I'm considering buying a cheap, short focal length eyepiece, as if I can make that work, it'll save me hundreds.

I don't know anything about eyepieces, as I started out doing astrophotography and have never done visual.
I just pulled an old 9mm GSO Plossl to bits - got a nice doublet with a focal length of about 16mm. Guess a 4mm Plossl would yield similar with a fl of about 7-8mm and that would refocus your focal plane at roughly 32mm further out (or a bit more if you want).

Edit: been thinking about it and suggest that you use the whole eyepiece (eg GSO). Unscrew the chrome extension tube and then you would need to get someone to turn down the eyepiece main barrel so that it fitted in the 1.25 inch guider tube (also would probably need to cut off the threaded bit) - that would give you a way of securely mounting the transfer lens in the OAG. If you can find where the guider focal plane is (using a small scrap of baking paper with a daylight scene), you can work out roughly where the transfer lens has to be. For a 4mm eyepiece, the distance from the original focal plane to the eyepiece will need to be about 8mm and the new focal plane will be another 8mm or so out on the other side of the lens.

The measures that you will need in order to work out the appropriate eyepiece focal length is the distance of the CCD from the front of the camera, the location of the existing focal plane in the OAG tube and how far out along the OAG tube you can move the camera.

Last edited by Shiraz; 03-07-2016 at 01:55 PM.
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Old 03-07-2016, 01:24 PM
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Thanks for taking the time Ray, really appreciate it! I've got some old measurements here for my focuser which tells me that it's about 2.7u per step and I think it needed to be about 7.5k steps further out, so that should mean I need about 20mm. I'll double check all of that before I order anything.

Edit: You corrected your post just as I was posting mine. So, based on those numbers, I should expect a change in focal plane ~4x the focal length of the doublet lens taken from a plossl. So if I need 20mm, and a plossl contains 2 doublets that are individually about twice their advertised length, I would need to divide the distance needed by about 8 and that should tell me (roughly) what eyepiece focal lengths I should look at... which gives me 2.5mm for 20mm, correct?

And by moving the lens element further away from the OAG prism, I would push the new focal plane out further, is that correct? I can only get it "so close" to the prism, maybe 20mm or so.
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Old 03-07-2016, 02:11 PM
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the distance from the old focal plane to the new one will be about 4x the fl of the lens, so if you use say a 5mm GSO plossl, you would move the focal plane out about 20mm. ie a cheap 5mm Plossl should do the job. However, there may be issues with getting spacing right (eg, can you get the lens close to the CCD), so you may need to go for a bit longer focal length - a 9mm Plossl would move the focal plane out by about 36mm and that may also be practical.

the key thing for getting the position right is to find out where the focal plane is now. If you get a small bit of baking paper and move it in and out of the OAG tube, you will be able to see by eye where the focal plane is if you image a daylight scene. You should then put the 5mm Plossl at about 10mm further out and you should get a transferred image another 10mm out (again you should be able to see the image using baking paper).

Can you get someone to turn down the barrel on an eyepiece? anyone with a small lathe could do it - you need not protect the thread.

What camera will you be using for guiding and how far back from the front of the camera/nosepiece is the ccd? If you use a long nosepiece, you might need to fit the Plossl within it.

it will involve a bit of messing around, but if it could possibly save you hundreds and a bit of time, it could be worth persevering

Edit, it may also be possible to swap your guide camera for one that fits down into the AOG tube, if that is the issue - what guide camera are you using?

Last edited by Shiraz; 03-07-2016 at 02:41 PM.
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  #418  
Old 05-07-2016, 05:03 PM
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Thanks Ray for all of your help, very much appreciate it. I decided in the end that buying an eyepiece and getting someone to machine it down probably wouldn't give me much change and might cause some annoying flex issues.

I went with another adapter, but realised I still only needed the one, so it's not as expensive as I'd feared, though still expensive enough.

On the bright side, your posts did lead me towards some simple little experiments with lenses and gave me a better understanding about them and how they work, so thanks again for that!
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Old 05-07-2016, 05:46 PM
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Quote:
Originally Posted by codemonkey View Post
Thanks Ray for all of your help, very much appreciate it. I decided in the end that buying an eyepiece and getting someone to machine it down probably wouldn't give me much change and might cause some annoying flex issues.

I went with another adapter, but realised I still only needed the one, so it's not as expensive as I'd feared, though still expensive enough.

On the bright side, your posts did lead me towards some simple little experiments with lenses and gave me a better understanding about them and how they work, so thanks again for that!
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  #420  
Old 20-07-2016, 10:14 AM
glend (Glen)
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New ASI1600 Update Version Aleady? & New Driver

I am hearing rumours that ZWO is about to ship a new version of the ASI1600 Cool camera, which will incorporate a USB hub socket in place of the old spot for the guide port. This is apparently to support/intergrate the ZWO filter wheel which is coming out as well.
There was a post on CN about it:

http://www.cloudynights.com/topic/54.../#entry7334930

I am not a member of Yahoo Group so I can't see the link they are talking about but maybe others can.

I am abit concerned about having a superceded model already, and there are not that many out there. Wonder if ZWO is going to retrofit the USB hub and case changes to previously sold models? No word on that. I hope they have beta tested the integrated USB hub with their new filter wheel, and other wheels (might be a problem there), and potential impacts on the still unresolved USB3 issues in the present software. Might be moving too fast.

I also have had a message on CN from Sam (ZWO) asking me to test a new ASCOM camera driver version - copy is attached here:

"can you test our new ASCOM driver and feedback
just to make sure the old strange bias problem won't happen in this version"
http://astronomy-ima...p V1.0.2.12.exe

I don't know exactly what the "old strange bias problem" is that he is referring to, anyone else know?
Its not likely I can test in the next week looking at the moon times and the weather forecast, but someone else might want to look at that driver release. I am happy enough with V1.0.2.5. which I am still running. Perhaps this new version also supports the USB hub port changes in the new version.
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