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Stowaway, 92TCC and corner stars
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Eckhard Völcker
I have been using my Mach2 on the Eagle peer with a 130 Starfire in a portable setup. - rough South Alignment with my iPhone compass - when it’s dark, 3 point polar alignment with NINA - NINA tells APPM to build a Dec Arc model for the target as part of the sequence Takes less than 30 minutes and the Dec Arc model makes guiding for exposure times under 5 minutes unnecessary. |
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Chris White
I would always optimize for luminance. Your color Dara can be blurred or aberrated and luminance used for details.
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Henry Kwok
Hi there
More update and more question I have used Nina Hocus Focus to tune my back focus distance, and determined that when using the Lum filter and the green filter, the optimal back focal distance is 67.9 mm (3.8 mm above the designed specification of 64.1 mm). Of this increase, only 0.3 mm can be attributed to the filter thickness (1mm). However, if I am using the red filter, the optimal distance is 0.7 mm less (67.2 mm). Conversely, when using the blue filter, the optimal distance is 0.7 mm more (68.6 mm) The filters are of the same ,are (Asronomik), series (Deep sky) and same thickness (1mm). I guess his implies that the corners / off axis optimal focal points are different for different wavelengths of light, which makes sense. My question is, shall I optimise the distance for Lum / green filter, or shall I optimise it for red or for the blue filter? This may be splitting hair but if I am making a custom adaptor I would like to get it as close to the best as possible. However, an alternative way is to make the adaptor at the shorter end and use shim if needed. Thanks |
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Bill Long
The Astronomik filters have been great. Both the Deep Sky RGB line, the Luminance (L2 in my case), and the MaxFR line. I have not used any other filters of theirs though. I think there are other brands that are 1mm that have all sorts of halo and field artifact
problems, mostly with their narrowband filters.
I have a set of the 3mm thick Chroma filters as well, and I have not seen much of a quality difference. Those are 3nm narrowband filters, which have some benefits over the 6nm ones in some cases. The color filters, I see no difference at all with.
From: main@ap-ug.groups.io <main@ap-ug.groups.io> on behalf of Chris White <chris.white@...>
Sent: Friday, August 5, 2022 3:13 PM To: main@ap-ug.groups.io <main@ap-ug.groups.io> Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars The good news is that all of the problems you've seen in 1mm thick filters were eliminated with the newest astronomk line.
Bill is using these filters with his epsilon and shared a recent ic1396 image he made. I'd challenge anyone to find anything deficient in the data that is filter related. He also shared a broadband image made with these newer astronomik filters and the same scope. Again, no filter artifacts. Sorry for the tangent. Ultimately it was to make the point that for a 1mm thick filter you only need to add 0.33 mm of additional spacing. |
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Chris White
The good news is that all of the problems you've seen in 1mm thick filters were eliminated with the newest astronomk line.
Bill is using these filters with his epsilon and shared a recent ic1396 image he made. I'd challenge anyone to find anything deficient in the data that is filter related. He also shared a broadband image made with these newer astronomik filters and the same scope. Again, no filter artifacts. Sorry for the tangent. Ultimately it was to make the point that for a 1mm thick filter you only need to add 0.33 mm of additional spacing. |
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Roland Christen
I have seen some strange artifacts in images taken by similar 1mm thick filters. I don't understand the point of making filters that thin. All the filters that I have used over many years are 3mm and none of them have ghost images or weird artifacts. Even the cheap ZWO filters that I'm using with their 6200 camera work well, except for the fact that they are not 3nm bandpass.
Rolando
-----Original Message-----
From: Henry Kwok <henry.ck.kwok@...> To: main@ap-ug.groups.io Sent: Fri, Aug 5, 2022 4:24 pm Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars I can attest to the quality of astronomik filters, which are 1mm thick. I use them as a much cheaper alternative to pricier ones delivering >95% of the performance. It does make it a pain to adjust for back focus as I have to add 0.3 mm - and because it is not in mm increment I always have to resort to some kind of shims.
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Henry Kwok
I can attest to the quality of astronomik filters, which are 1mm thick. I use them as a much cheaper alternative to pricier ones delivering >95% of the performance. It does make it a pain to adjust for back focus as I have to add 0.3 mm - and because it is not in mm increment I always have to resort to some kind of shims.
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ROBERT WYNNE
I think what I got this post was that 1mm filters are like trying to polish a potato chip. That is to say it can be done but at a non value added expense to performance. Not that the end result of polishing a potato chip perfectly flat would end up being like a potato chip. They probably are great performers but very difficult to polish. Once polished flat, a 1mm filter will remain flat to the extent thermal expansion allows. -Best, Robert
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Chris White
On Thu, Aug 4, 2022 at 10:49 PM, Roland Christen wrote:
The astronomik deep sky rgb and max fr filters are excellent and only 1mm thick. Not a potato chip and proven performers even with f3 systems. |
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Roland Christen
Those cover glasses are 3mm thick. 1mm glass is extremely hard to polish flat. It's like trying to polish a potato chip. I have 3mm thick filters on my cameras.
Rolando
-----Original Message-----
From: Emilio J. Robau, P.E. <ejr@...> To: main@ap-ug.groups.io Sent: Thu, Aug 4, 2022 9:30 pm Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars Chris,
We have been reading the same threads. The two items Roland points out that are interesting is the glass for the chamber cover and the glass on the chip itslf. I thought of those but I didn't if you know what I mean because I think this is the first time I have focused on those pieces of glass. Are they really 1mm thick? We may be splitting hairs here and the point is that your adjustment mibht be a little further than the spec? How about on the short side? Anyone coming up consistently short? I keep having to add just a little to the back spacing spec. |
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Chris,
We have been reading the same threads. The two items Roland points out that are interesting is the glass for the chamber cover and the glass on the chip itslf. I thought of those but I didn't if you know what I mean because I think this is the first time I have focused on those pieces of glass. Are they really 1mm thick? We may be splitting hairs here and the point is that your adjustment mibht be a little further than the spec? How about on the short side? Anyone coming up consistently short? I keep having to add just a little to the back spacing spec. |
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Chris White
On Thu, Aug 4, 2022 at 06:11 PM, Roland Christen wrote:
There are some really nice filters out there now that are only 1mm thick. It is my understanding that you only add 1/3 the thickness of the glass as spacing. So a 3mm thick filter would be 1mm of additional spacing needed, but a 1mm thick filter would only require 0.33mm. |
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Roland Christen
The use of filters requires 1mm increase in back focus per filter. Also 1mm more is needed for camera entrance glass, unless the camera manufacturer takes it into account. There is also a cover over the actual chip which also would need a 1mm increase.
Roland
-----Original Message-----
From: Luca Marinelli <photo@...> To: main@ap-ug.groups.io <main@ap-ug.groups.io> Sent: Thu, Aug 4, 2022 4:57 pm Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars Hi Henry,
I recently optimized backfocus on a Stowaway with Hocus Focus and an ASI6200 as well and curvature null was achieved several mms past the nominal backfocus distance with the flattener (not the TCC – I haven’t tested that yet). That’s one
reason why I had asked the question about definition of optimal backfocus adopted by Roland. Minimum off-axis spot size will depend on how far off-axis it is measured and depending on the size of the sensor curvature null may not correspond exactly to the
same backfocus distance so it’s not too surprising that the measurements differ by a few millimeters.
Luca
From: main@ap-ug.groups.io <main@ap-ug.groups.io>
On Behalf Of Brian Valente via groups.io
Sent: Thursday, August 4, 2022 5:00 PM To: main@ap-ug.groups.io Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars Hi Henry
I can't speak specifically to the Stowaway, but in my experience backfocus can vary by mms on virtually all my setups, and it's a fact of life.
I always test backfocus distance with new installs, and even with refractors the actual distance for ideal backfocus can and does vary from the published details
I find it's hard to argue with the results especially if they are what you describe (i.e., much better with different bf distance)
Brian
On Thu, Aug 4, 2022 at 12:43 PM Henry Kwok <henry.ck.kwok@...> wrote:
--
Brian
Brian Valente
astro portfolio https://www.brianvalentephotography.com/astrophotography/
portfolio
brianvalentephotography.com
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Luca Marinelli
Hi Henry,
I recently optimized backfocus on a Stowaway with Hocus Focus and an ASI6200 as well and curvature null was achieved several mms past the nominal backfocus distance with the flattener (not the TCC – I haven’t tested that yet). That’s one reason why I had asked the question about definition of optimal backfocus adopted by Roland. Minimum off-axis spot size will depend on how far off-axis it is measured and depending on the size of the sensor curvature null may not correspond exactly to the same backfocus distance so it’s not too surprising that the measurements differ by a few millimeters.
Luca
From: main@ap-ug.groups.io <main@ap-ug.groups.io>
On Behalf Of Brian Valente via groups.io
Sent: Thursday, August 4, 2022 5:00 PM To: main@ap-ug.groups.io Subject: Re: [ap-ug] Stowaway, 92TCC and corner stars
Hi Henry
I can't speak specifically to the Stowaway, but in my experience backfocus can vary by mms on virtually all my setups, and it's a fact of life.
I always test backfocus distance with new installs, and even with refractors the actual distance for ideal backfocus can and does vary from the published details
I find it's hard to argue with the results especially if they are what you describe (i.e., much better with different bf distance)
Brian
On Thu, Aug 4, 2022 at 12:43 PM Henry Kwok <henry.ck.kwok@...> wrote:
-- Brian
Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com |
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Chris White
I agree with Brian. Backspacing is a target but it can vary slightly from specification for an optimal field. Additionally, some camera manufacturers specify chip setback as +/- 0.5mm from specifications. So you might not be able to depend on that spec as gospel.
I found with my Stowaway and aps-c qhy camera that it was very close to AP specification of 64.1mm Also don't forget to add 1/3 the thickness of your filter or any other glass in the image train that is not accounted for. |
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Hi Henry I can't speak specifically to the Stowaway, but in my experience backfocus can vary by mms on virtually all my setups, and it's a fact of life. I always test backfocus distance with new installs, and even with refractors the actual distance for ideal backfocus can and does vary from the published details I find it's hard to argue with the results especially if they are what you describe (i.e., much better with different bf distance) Brian On Thu, Aug 4, 2022 at 12:43 PM Henry Kwok <henry.ck.kwok@...> wrote:
--
Brian Brian Valente astro portfolio https://www.brianvalentephotography.com/astrophotography/ portfolio brianvalentephotography.com |
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ROBERT WYNNE
That's what I thought as well. Mike is the Michaelangelo of Excel. -Best, Robert
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Henry Kwok
Hello all again
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Cheng-Yang Tan
Hi Mike, Your drawings in Excel look excellent. I thought you had drawn them in a CAD program! Personally, I wouldn't use Excel to draw anything, because I have other drawing tools. But it's interesting to see that Excel is capable of doing it. cytan
On Wednesday, August 3, 2022 at 09:58:36 PM CDT, M Hambrick <mhambrick563@...> wrote:
Hi Robert Here is the Excel version of my drawing file. I learned how to make my drawings on Excel out of frustration from trying to make drawings on Powerpoint. I discovered that it was possible to make really accurate and detailed drawings on Excel, then just cut and paste them onto my Powerpoint slides. I format the spreadsheet rows and columns so that they are the same size in number of pixels. For my version of Excel and screen resolution a row height of 15.00 and column width of 2.00 gives a 25 X 25-pixel grid. if you draw an object like a line, you can select it and use the arrow keys to move it. You can use the size and position menu to tweak the size and angular position of objects. The Format toolbar has the drawing tools. As for the drawings themselves, I started making them to document the position of the dovetail slides and counterweights for my different imaging setups. I have three different imaging scopes: The Stowaway, a Tele-Vue NP101is, and a 180EDT. There is a set of drawings for each system, and as you can see on these drawings, multiple setups for each. I have been using a separate guide scope and camera in a piggyback arrangement since I started out, but I have decided that the piggyback arrangement may be causing a lot of differential flexure, so last year I converted all of my imaging systems over to side-by-side. It is more complicated, but easier to get precisely balanced, and hopefully less prone to flexure. So far, the only system I have actually used for imaging in the side-by-side arrangement is the 180EDT. Based on the results I have seen so far; I have concluded that I need to switch to an off-axis guiding system. I am currently working on getting the 180EDT set up for that. I also want to try my luck at building a pointing model, but I am not sure how well a model will work with my portable setup that I set up and take down every night. Of course, I am hopeful that I will be lucky enough to have my name drawn for one of the new 110 GTX scopes so that I can make another set of drawings. Mike |
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ROBERT WYNNE
There's a lot of work and devotion to this singularly unique approach to drafting components. What drove you to Excel other than disatisfaction with Powerpoint rather than off the shelf drafting software? In my past, the corporate classes taught diferent software for those working in applicable disciplines. I stopped Excel training at regression analysis (I think I was getting slightly in over my head) while I decided it might be to my advantage to learn rudimentary drafting software. That began with a 2D program called Canvas, then onto CADKEY which was not widely used by most of my vendors and finally and most satisfying SolidWorks. SW is a true 3D software and allows finite element analysis so you can determine when your component will fail among many other features. That and it plugs in neatly to most CNC software eliminating the need to translate drawing specs to machine programming. But I certaintly never thought Excel could be as productive as you have made it. You must have very high abstract relational reasoning to arrive at this solution to drafting. -Best, Robert
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