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Not many chances of Solar Imaging this year so far but caught this one.
AR2741 from the 12th late afternoon
152mm Technosky Refractor @ f5.9
135mm Baader D-ERF
Daystar Quark Chromosphere + Eliminator
5862 Frames, 4Ms 30 second capture @ 195Fps 1024 x 768 Mono16
Best 45% Frames stacked in AS!3, ImPPG then tweaked in PS
I have 7x 36mm Baader filters in my QHY Filter wheel. I use a simple Orion 80ED with a manual focuser. I have two questions basically.
a) How important is refocusing between the LRGB Ha OIII and SII filters?
b) If important, then how do I manually calculate the offset distance between them assuming the filters aren't parfocal?
Rather than add this test to my original thread regarding the scope findings I started a new thread here to describe my findings and measurements using a Baader M56 Click-Lock. Unlike other SW ED Pro offerings, the focuser unit that is supplied with the new SW ED 150 has no provision for rotation during use. In addition, I noticed that despite there being a total of 142mm of travel in the draw tube, the majority of my EPs focus at the near end of travel and I was concerned there may be a lack of in-focus provision.
I contacted @FLO and asked them for technical details of the Baader M56 Click-Lock particularly the loss of in-focus during use. (I have previously owned a similar device for use with a 9.25" SCT which adds ease of use, a rotation facility and superb security to all attachments). FLO very kindly reciprocated and provided one for testing. Here I present some results of that test.
Essentially, use of the Click-Lock with EPs (+/- a TV Powermate) results in a loss of 12.5mm of in-focus. For the EPs tested here that was not an issue. The stock SW focuser comes with a 2"adapter with two grip screws and a locking ring. Please note that removal of the locking ring when using the Click-Lock does not assist with reducing loss of in-focus since the Click-Lock internal flange sets before reaching the locking ring.
You can see that my ES 14mm EP inserted into the 2X Powermate was the only combination that did not reach focus (it almost did but not quite). The 2X is a 2" Powermate and I had to use the 1.25" insert which adds about 8mm of depth. the Powermate also does not seat fully in my WO diagonal.
I also tested two planetary cameras (+/- 2" TV Powermate) which focused well within the full range of the draw tube extension maximum which is 142mm. Use of the Click-Lock provides a very secure and flexible adaptation to the standard SW focuser adapter and most importantly allows easy rotation of diagonal and camera. For me, this is a must have accessory for this scope. Its easy to use with gloves too!
Standard SW set up:
Click-Lock set up:
Addition of a 2.5X Powermate:
Planetary camera and 2x Powermate set up:
In addition I used the locking screw whilst observing the live star image of Alpheratz on screen through the Bhatinov mask. There was absolutely no change in the focus position as I tightened/loosened the locking screw. This last set up I also tested at near vertical (Deneb) and there was no slip at all in the focuser control. Action was firm and smooth throughout the length of the draw tube.
For the original scope test go here:
I recently tried imaging M7 with my 6" f/4 Newtonian. I had earlier commimated it with a Cheshire and Howie Glatter and was sure of the collimation. However, when I imaged using my DSLR with the coma corrector installed, I get focused stars off centre and not on the optical axis. Anyone experience anything similar before? What could this be? Tilt in the optical train? The focuser was drawn out only about 5mm to reach focus along with a 50mm extension tube. Any suggestion is welcome.
By Anthony RS
I bought a GSO 2 inch Coma Corrector for my 8inch Newtonian. I'm still having terrible coma on one of the corners which is actually worse than without the coma. The rest of the corners look fine with proper guiding.
Here are some details and what I've done to try and solve the issue:
1- Spacing is 75 mm just as recommended.
2- Used a Cheshire, laser collimator, and a webcam to check collimation.
3- Squared the focuser so that it's orthogonal to the optical axis.
4- Tried another DSLR
Note that once I collimate and double check that I'm collimated with all the tools, I always try to do a star test and collimation appears off (the dark spot isn't in the middle). Last time I tried to collimate the primary using a star but it's really tough to fine tune since due to the focuser's sag, I can't be sure that the star is in the middle of the fov.
My take on the problem is that when I'm using the DSLR with the coma corrector, the weight is moving the focuser away from the center of the optical axis but I'm not sure this if this is the case. I've tried everything and I'm out of ideas.
Below is a test image I took for Lagoon Nebula. Notice the coma on the left top side mostly, while the right side usually appear to have no coma (not the case in the attached image though for some reason, but usually the right side is fine). One more thing I've noticed, the stars on the left corner appear to be out of focus while the rest of the image appears well in focus (used a Bahtinov mask with APT bahitnov focus tool)
There's also another image I took for a distant light to check collimation (since clouds covered the sky as soon as I decided to do a star test). It appears to be fine and I was able to center it better but didn't capture the image.
Please let me know if you have any idea what's causing this. My number one suspect is the focuser's sag preventing me from doing accurate collimation although everything appears to be normal while collimating. I'm giving this another 2 weeks of my time, if it doesn't work I might quit astrophotography till I'm able to afford an APO.
One more thing that needs to be added, when using the GSO CC I had to move the primary mirror up the scope by around 2 cm to be able to achieve focus.