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Old 06-05-2015, 10:49 AM
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PRejto (Peter)
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Poor Man's Rotator?

My setup involves two TEC refractors on the same mount. My idea is to image with both at the same time, luminance on one, RGB the other. So far automating this has been anything but simple but I have made a lot of progress.

A real issue is the lack of ability to rotate cameras which I need to frame objects of interest. Doing this manually for 2 cameras is quite hard and time consuming. Since I use an ONG to guide I don't need to rotate in order to guide. But the framing issue is real for large targets or those spread apart (like Leo Triplet, etc). My rectangular chips are often not aligned to best advantage.

I have gone through a protracted exercise to see if I could add two rotators. The answer is a very qualified "maybe." In the end it would be very expensive, add significant weight, and lots of complication. So, I've decided not to go down that path.

However, I am thinking I could simplify life somewhat if I could take advantage of the two built in focuser rotators built into both TEC scopes. All that is missing is some sort of graduated scale in degrees. So I'm looking for ideas about how something could be added to the tubes of the TECs? The unused finder brackets could hold a pointer with a scale wrapped around the scope tube. But this isn't exactly in stock at the local hardware store....

Another idea might be to use some sort of digital protractor like this:

http://www.aliexpress.com/item/Free-...394624326.html

Having never used such a device I imagine it could only work if gravity is perpendicular to the device which "might" mean I'd need to orient the scopes horizontal every time I wanted to move the rotators which is not ideal. Perhaps I'm wrong about this. I'm looking for any additional ideas, mechanical or electrical which could assist in easier hand rotation.

Many thanks!

Peter
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Old 06-05-2015, 11:49 AM
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Here you go:

http://www.alibaba.com/showroom/flex...ale-ruler.html

Greg.
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Old 06-05-2015, 11:53 AM
jase (Jason)
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You see Peter... now you are getting all fancy with a digital protractor. This starts to no longer sound like a poor man's rotator.

If you want to do this on the cheap and even simpler. Just plate solve one of the scopes to find out the camera position angle. Then do the same for the second scope and keep rotating the camera until you get the position angles aligned.

Put a piece of masking tape on the rotator and camera so if you remove the camera's you can quickly visually align then double check via plate solves before imaging again. If cable wrap is an issue for one camera, just flip it 180 degrees from the position angle value of the other scope. sub registration will sort out the reset.

I think I would be more worried about getting the scopes perfectly parallel so that they are imaging the exact same field of view. Again, plate solving can assist you there. You want to ensure that when you plate solve to get the fov center in RA and DEC, that that same RA and DEC is the center (or near to) on the other scope.

If one scope has a wider field of view, do the RGB with this instrument. You want the higher resolution from the longer focal length so the lum from a narrower field of view.
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Old 06-05-2015, 12:30 PM
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If you can get the RGB field to be sufficiently bigger than the Lum field, then you don't have to worry at all, just coregister the RGB to match the Lum when processing the LRGB

Mike
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Old 06-05-2015, 02:16 PM
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Quote:
Originally Posted by gregbradley View Post
Thanks, Greg. Pretty simple idea if the ruler is flexible enough to mount. But, having actual degree of rotation marks would make it much easier to move to an exact position without doing a little math. Still, this would be the simple answer.

Peter
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Old 06-05-2015, 02:21 PM
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Quote:
Originally Posted by jase View Post
You see Peter... now you are getting all fancy with a digital protractor. This starts to no longer sound like a poor man's rotator.

If you want to do this on the cheap and even simpler. Just plate solve one of the scopes to find out the camera position angle. Then do the same for the second scope and keep rotating the camera until you get the position angles aligned.

Put a piece of masking tape on the rotator and camera so if you remove the camera's you can quickly visually align then double check via plate solves before imaging again. If cable wrap is an issue for one camera, just flip it 180 degrees from the position angle value of the other scope. sub registration will sort out the reset.

I think I would be more worried about getting the scopes perfectly parallel so that they are imaging the exact same field of view. Again, plate solving can assist you there. You want to ensure that when you plate solve to get the fov center in RA and DEC, that that same RA and DEC is the center (or near to) on the other scope.

If one scope has a wider field of view, do the RGB with this instrument. You want the higher resolution from the longer focal length so the lum from a narrower field of view.
Jason,

Thanks for your input! The procedure you outline is already exactly what I do and it takes forever! I have an Optec Libre on the TEC 140 so my fields are perfectly aligned. I just want a very simple direct way to move each camera the same number of degrees so there is no initial guessing. After that I'm sure I would refine the motion of scope 2 with a plate solve or two.

Peter
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Old 06-05-2015, 02:26 PM
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Quote:
Originally Posted by strongmanmike View Post
If you can get the RGB field to be sufficiently bigger than the Lum field, then you don't have to worry at all, just coregister the RGB to match the Lum when processing the LRGB

Mike
And Mike, you are the devil that started me down this path. Yikes so many issues but many close to being solved. I have custom piece of software that allows me to sync both cameras so I can dither and automate using CCDAP. And focus max v4 has an acquire star function for dual focusers. It works but still has a bug when connected to CCDAP. So, I'm very close. Unfortunately the larger field (not by much) is the TEC 180 doing luminance. This is the higher resolution scope so I think that makes sense. So far this arrangement is giving really good results.

Peter
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Old 06-05-2015, 02:39 PM
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Quote:
Originally Posted by PRejto View Post
And Mike, you are the devil that started me down this path. Yikes so many issues but many close to being solved. I have custom piece of software that allows me to sync both cameras so I can dither and automate using CCDAP. And focus max v4 has an acquire star function for dual focusers. It works but still has a bug when connected to CCDAP. So, I'm very close. Unfortunately the larger field (not by much) is the TEC 180 doing luminance. This is the higher resolution scope so I think that makes sense. So far this arrangement is giving really good results.

Peter
You are quite right, I was thinking that but didn't do the calcs because I am at work and was being a bit brief ...That custom software that allows synching/dithering with two cameras sounds like the smoking gun really, remember it is really only the Lum that needs to be perfect, the RGB can be pretty ordinary and LRGB still works very well (unless you want to be able to construct synthetic Lums of course). Once running to your liking you will have a formidable outfit Pete....so sorry

Mike
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Old 06-05-2015, 04:44 PM
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You could always put a rotator on just one of the scopes and use it to match the orientation of the other. That's a half (arsed) solution

I sometimes use plate solving to match camera orientation between imaging sessions and I don't find it takes me too many attempts to get close enough.

Cheers,
Rick.
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Old 06-05-2015, 05:33 PM
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You could always put a rotator on just one of the scopes and use it to match the orientation of the other. That's a half (arsed) solution

........
Cheers,
Rick.
That's the solution I was thinking about and would do if you cannot afford two rotators. There is a 3" rotator in the for sale section that Eric has for sale.
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Old 06-05-2015, 06:49 PM
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You could use 2 x Tokometer style rotators, adapted to your scope. If you didn't already have manual rotators on the TECs, this would have worked: http://www.optcorp.com/an-tak-pkg-ro...tml#noredirect

The Takometer itself isn't cheap, but if you had 2 x robofocus controllers you could rig something up: http://www.optcorp.com/astrodon-tako...efractors.html

Hope this helps...
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Old 06-05-2015, 06:59 PM
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You could easily build something with a takometer,small stepper motor, an arduino microprocessor and an easydriver motor controller board. Would cost maybe $30(not including the takometer)in parts, a bit of time to build and a basic bit of programming.. The only real expense would be the takometer..

Would operate much like the one posted above but without the expense of a robofocus kit.
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Old 06-05-2015, 07:10 PM
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Quote:
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That's the solution I was thinking about and would do if you cannot afford two rotators. There is a 3" rotator in the for sale section that Eric has for sale.

Funny you mention that Paul! Though Eric might not think so. I've been asking him a million questions about fitting it to the TEC 180. It might fit but would leave quite minimal BF...focusing with FM might be pretty hard or compromised as a result. Eric has been great and patient with me.

Peter
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Old 06-05-2015, 07:33 PM
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I bought a Tak CAA and machined an adapter to fit it to my imaging train, then to get the rotation angles I divided up the diameter of a part of the imaging train into 360 deg, drew this scale on a strip of paper and wrapped it around the tube and stick it on with clear sticky tape (plenty). Plate solved an image then put a second marker on the tube that doesn't rotate at the mark indicated by the plate solve.
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Old 06-05-2015, 08:28 PM
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Peter I've been using a digital inclinometer in the manner you describe for years with great success. I generally put it on the top (or side) of the cooling assembly of my QHY9 while parked, then rotate the camera and FW assembly to the PA figured out earlier in pre-capture planning. Check PA with plate solving later, but very rare to not be within 1-3 degrees of where it should be.

They're great things to have in the field, or for zeroing dec axis on cheaper mounts anyway.
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Old 07-05-2015, 07:21 AM
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Josh, Alex and Logan,

Thanks for the suggestion of the TAKometer. A couple of years ago I wrote to Don Goldman and asked him if he thought the unit could be adapted to my TEC 140. He thought not, but I think you guys would say yes it can. I wasn't confident enough about the actual part sizes to take the plunge and I guess I'm still not. My scopes have 3" focusers, not 4". Wouldn't that make this quite tricky? I'd still prefer a solution I could operate without touching the scope. In the meantime I'm fabricating a printed solution to wrap around the TEC tubes.

Thanks,

Peter
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Old 07-05-2015, 10:43 AM
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Sorry Peter, not much help here but I was just looking at your outfit now and man, really looks awesome mate, oodles of very capable quality there. I particularly like the table lamp with shade on the deck - very quaint

Mike
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Old 08-05-2015, 05:01 PM
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. I particularly like the table lamp with shade on the deck - very quaint
Mike
Mike, I spent so much money on gear the lamp was all I could afford!

Below, my attempt to add rotation angles to the TEC180. I used a flexible aluminium band, some felt, and had the scale printed on Tyvek. The Tyvek will last but not sure about the print. Perhaps I can coat it with a clear lacquer. The pointer is crude but perhaps good enough. I'll build up the TEC140 model tomorrow.

Peter
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