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Re: Back Focus Troubles #Absolute_Encoders

Andrew J
 

Hi Jeff.

You are right, I picked a bad example. I remembered after my initial post that the FF on the TEC140ED moves with the focuser and because it is the last correcting element before the sensor means that the distance between this element and the sensor will not change when the focuser is repositioned. So, again bad example.  My understanding is that the back focus is determined by the LAST correcting element in the light path before the camera sensor. Therefore, I should have used the example of the TEC140ED without the FF which I think has a recommended BF of 170mm.

Another example I am familiar with is the Celestron EDGE HD scopes that have a correcting element in the baffle tube of the scope. Celestron states in their Edge HD White Paper that back focus for the EDGE HD 925, 1100, 1400 is 146.05mm. However, it is fairly common for people to add Crayford focusers to the back of the EDGE HD scopes and lock the primary mirrors. In this case the last correcting element does not move with the focuser and distance between the last correcting element and the sensor will change as the focuser is repositioned. In examples where the last correcting element does not move, why is dialing in a specific back focus distance using spacers so critical if the distance is going to change depending on the position of the focuser?

Andrew
Re: Back Focus Troubles #Absolute_Encoders

Andrew J
 

Hi Linwood.

Thanks for the OPT link. I hadn't seen that before and is quite helpful. I have book marked it for future reference. 

Andrew
Re: Will the Mach 2 support .....

Luca Marinelli
 

Thank you for sharing your results, Roland. I was imaging with the Mach2 and my solid tube 10in f4 reflector last night (40lbs fully loaded but with a fairly significant moment arm) and the absolute encoders on the mount make it track smoother and easier than when I use the same scope on my AP1100 without encoders. The difference encoders make in ease of use of a mount is truly remarkable. Obviously imaging results are the same, provided one guides the non-encoder mount appropriately, but it certainly takes a bit more finesse and knowledge with the non-encoder mount.

With regards to the comparison between the QSI683 and the ZWO 6200MC, I wanted to offer some considerations to keep in mind:

1) In spite of the larger diameter of the 160mm optics, the etendue per pixel is 1.76x larger for the 130mm scope given the bigger effective pixel size of the binned KAF8300 sensor. This means that the solid angle of sky seen by each pixel of the KAF8300 sensor  is almost twice as big as the ZWO 6200MC system and signal will accumulate accordingly, even before taking into account quantum efficiency.
2) The ZWO 6200MC has a Bayer matrix in front of the signal. You did not mention what filter you were using with the QSI683 camera but if it was a luminance filter, you are allowing up to about 4x more wavelength bandpass than any of the R, G, or B filters in front of each of the pixels of the ZWO ASI6200MC.
3) The ZWO 6200MC is a variable gain camera. You did not mention what gain setting you were using. If you were using the camera with default gain in the ASCOM driver, it is probably gain 0 (CMOS gain 0.8 e/ADU), which corresponds to the highest full well capacity and dynamic range, but the lowest sensitivity of the camera (signal accumulation measured in ADU per unit time). It should be noted that the camera circuitry changes acquisition mode at gain 100 (CMOS gain 0.28 e/ADU) with a step change in read noise from 3.5e to 1.5e per read. This is a particularly useful gain setting when large full well capacity is not the paramount concern.

Best,

Luca
Re: Will the Mach 2 support

Harley Davidson
 

Thanks for the information and photo Roland!

tony

On 6/1/2021 8:06 PM, Roland Christen via groups.io wrote:
Hello AstroNuts,

We get this question many times, "will the Mach2 support my scope, camera etc." I can't really answer specific setups since I don't have infinite variety of scopes at my disposal. However, to give you some idea I am presently testing two scopes piggybacked on the Mach2.

Here is my present setup. I am using it to test various optics, cameras and field flatteners. It consists of a 160EDF refractor with QTCC and a full frame ZWO 6200 color camera, which provides a very wide field. On top rides an oldie but excellent 130 EDF refractor with 2.7" focuser, 67PF562 Flattener and my QSI 683WSG camera, Lodestar off-axis guider and an 8x50 Baader finder for good measure. Both scopes sit in rings that are attached to dovetail plates. When you add up all the parts, the whole shebang weighs close to 70 lb with the weight centered about 9 inches from the top of the Dec axis. I have approximately 75lb worth of counterweight which includes the weight of the standard Mach2 cwt bar and the shorter extension.

Is it stable and does it slew, track and guide effortlessly? Yes on all counts. It does need to be closely balanced, but not ridiculously so. Using MaximDL6, in poor seeing i get on the order of 0.4 arc sec rms guiding. In good to excellent seeing I get 0.1 to 0.15 arc sec rms guiding. My guide exposure is between 2 and 5 seconds with 1.5 seconds between exposures. Best guiding seems to be when the exposures are 4 to 5 seconds, and I get very few excursions that are larger than 0.5 arc sec pk.

By the way, I don't usually guide with one scope and image with another. In this case I am guiding with the lighter weight 130EDF and I am getting perfect round stars with the 160 below. The 160 is shooting at 960mm focal length with a 3.75 micron/pixel camera, 0.8 arc sec per pixel. ZWO 6200 camera. resolution with this camera in medium seeing has yielded 1.4 arc sec FWHM stars in a 5 minute exposure.

I will be shooting tonight if the weather holds, and I can record some guide graphs for anyone interested. Seeing is supposed to be good (4 out of 5) but transparency will be poor. I'm doing a shootout between the CMOS camera with 3.75 micron pixels and my older QSI683 CCD camera with 5.4 micron pixels. Which camera records images faster? Which has better contrast? Any bets on the winner?

Rolando


--
Roland Christen
Astro-Physics

Re: VIDEO - Mach2 Right Ascension Belt Adjustment

Harley Davidson
 

Thank you Mike!

tony

On 6/1/2021 7:34 PM, M Hambrick wrote:
Another great video Tony.

Like you, I have always been impressed to see how A-P machines so many of their parts from solid aluminum bar stock. 

That cogged belt is also impressive. The part number indicates that it is a 3 mm pitch belt. What is the width ? I am guessing that it is at least 3/8" wide. That seems to be more than strong enough for the application.

Mike

Re: Question: How do I safety replace the CW shaft adapter (got it off, grease?)

Konstantin von Poschinger
 

Hi,

if you have trouble loosing the counter weight shaft, use a mounted counter weight and turn that till the shaft get loosened!

Grüsse

Konstantin


Konstantin v. Poschinger


Hammerichstr. 5
22605 Hamburg
040/8805747
0171/1983476

Am 02.06.2021 um 03:39 schrieb Roger Howard <cargostick@...>:

1100GTO.  I got it free with the help of my neighbor, but just wanted to post that I used some lube on the insert to hopefully keep it from happening again.  Yes, I do have the insert.

Re: Will the Mach 2 support .....

Roland Christen
 

Result #2: Tracking with 2 refractors piggyback

The sky unfortunately was not pristine during my imaging session. High level clouds continued to drift thru the image, so the tracking was at times a bit unsteady, but overall not too bad. Here is one tracking graph that was typical of the evening. 1 pixel = 1.45 arc sec in this graph. In this 15 minute period the tracking was less than 0.5 arc sec pk, and approx 0.14 arc sec rms.

Rolando





-----Original Message-----
From: Roland Christen via groups.io <chris1011@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Tue, Jun 1, 2021 11:47 pm
Subject: Re: [ap-gto] Will the Mach 2 support .....

Result #1: CMOS vs CCD

The 683 has an 8300 chip that's not very efficient but it's monochrome. There are better CCD chips with much higher quantum efficiency such as the Starlight Xpress Pro36, which is a full frame camera with exceptional low noise. It has a 7.4 micron pixel size.

The ZWO 6200C is a color CMOS camera with very low noise, but is it as sensitive as a monochrome CCD? It turns out that it isn't as sensitive as the 8300 monochrome chip. In a side by side test of these two cameras, the ZWO produced a peak intensity of the core of M106 that was only 75% as high as the QSI camera. And that's with a 50% greater light grasp of the 160 EDF vs the 130 EDF that the QSI was attached to. The CMOS did have a signal/noise advantage because of the low noise chip, but part of that was due to the higher light grasp of the 160 mm aperture.

See image below:
Rolando


--
Roland Christen
Astro-Physics
Re: Will the Mach 2 support .....

Roland Christen
 

Result #1: CMOS vs CCD

The 683 has an 8300 chip that's not very efficient but it's monochrome. There are better CCD chips with much higher quantum efficiency such as the Starlight Xpress Pro36, which is a full frame camera with exceptional low noise. It has a 7.4 micron pixel size.

The ZWO 6200C is a color CMOS camera with very low noise, but is it as sensitive as a monochrome CCD? It turns out that it isn't as sensitive as the 8300 monochrome chip. In a side by side test of these two cameras, the ZWO produced a peak intensity of the core of M106 that was only 75% as high as the QSI camera. And that's with a 50% greater light grasp of the 160 EDF vs the 130 EDF that the QSI was attached to. The CMOS did have a signal/noise advantage because of the low noise chip, but part of that was due to the higher light grasp of the 160 mm aperture.

See image below:
Rolando





-----Original Message-----
From: M Hambrick <mhambrick563@...>
To: main@ap-gto.groups.io
Sent: Tue, Jun 1, 2021 7:51 pm
Subject: Re: [ap-gto] Will the Mach 2 support .....

Thanks for showing us this imaging setup Roland, and yes, please share your results including your guiding graphs.

Mike

--
Roland Christen
Astro-Physics
Re: Will the Mach 2 support .....

Roland Christen
 

Yes indeed. In fact I have run it both with a model and with guiding. The model tracks a bit smoother since it's not chasing a twinkling star. But the outcome is the same.

Rolando



-----Original Message-----
From: Greg McCall <emailgregnow@...>
To: main@ap-gto.groups.io
Sent: Tue, Jun 1, 2021 9:08 pm
Subject: Re: [ap-gto] Will the Mach 2 support .....

Hi, would that setup still be OK if you built and loaded a tracking model from APPM in place of guiding?

--
Roland Christen
Astro-Physics
Re: Mach 1 ra motor failure to move the the west.

crib409acme425
 

thanks Roland , I will keep this in mind.  Chuck 
Re: Problems using ASI air pro and AP mounts

Kenneth Tan
 

Thx! 

On Wed, 2 Jun 2021 at 05:53, Kevin Cook <kvc3509@...> wrote:
Ken - One thing I discovered about the ASIAIR version of PhD guiding is that you have to set the guiding rate to 1X in TWO places - on the AP hand controller keypad (or on AP mount software if using that) and on the ASIAIR pull-out tab (it pulls out to the left from the right-side vertical control panel).  This ASIAIR pull-out tab is the same one you use to select your target and direct a GOTO.  The guiding rate needs to be set at 1X in both places or the guiding is all over the place.   Kevin

On Tue, Jun 1, 2021 at 2:32 PM Kenneth Tan <ktanhs@...> wrote:
Hmm I wonder if there is something wrong with my setup. I use a 250 mm fl guide scope with an ASI 1290 cam as guidecam

On Wed, 2 Jun 2021 at 05:29, marsh.family <marsh.family@...> wrote:
Hi Kenneth

I've had very unpredictable guiding performance with AsiAir Pro until the latest version with multi star guiding. 

I haven't had too many chances to test it out but the guiding was very good when I did. Better then the best with the previous version. And seemingly more stable. I just started it up and it worked. No tweaking. 

Chris



Sent from my Galaxy


-------- Original message --------
From: Kenneth Tan <ktanhs@...>
Date: 2021-06-01 5:21 p.m. (GMT-05:00)
Subject: [ap-gto] Problems using ASI air pro and AP mounts

I have a strange problem. I am using a c925 on a AP 1600 . I can run it without guiding for about 30 s with fairly round stars.  The moment i try to guide with the phd on the asiair pro, it is all over the place. Unpredictable spikes in both axes.  Has anyone encountered this problem? I will try with phd proper the next time.
 
Kenneth
Re: Question: How do I safety replace the CW shaft adapter (got it off, grease?)

W Hilmo
 

That was exactly how I read it the first time…

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Roland Christen via groups.io
Sent: Tuesday, June 1, 2021 6:46 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Question: How do I safety replace the CW shaft adapter (got it off, grease?)

 

WoW, you have a generous neighbor to give you a mount for free. Stuck out tongue winking eye

 

Rolando

 

-----Original Message-----
From: Roger Howard <cargostick@...>
To: main@ap-gto.groups.io
Sent: Tue, Jun 1, 2021 8:39 pm
Subject: Re: [ap-gto] Question: How do I safety replace the CW shaft adapter (got it off, grease?)

1100GTO.  I got it free with the help of my neighbor, but just wanted to post that I used some lube on the insert to hopefully keep it from happening again.  Yes, I do have the insert.


--
Roland Christen
Astro-Physics

Re: Problems using ASI air pro and AP mounts

Worsel
 

Kenneth

One advantage to using PHD2 proper versus the PHD version built into the ASIAIR is that you can post your Guide and Debug logs on the PHD2 forum

https://groups.google.com/g/open-phd-guiding

See How to ask for help with PHD2

The PHD2 forum cannot possibly provide insight on modifications that others make to the open source code.

Bryan
Re: Will the Mach 2 support .....

Greg McCall
 

Hi, would that setup still be OK if you built and loaded a tracking model from APPM in place of guiding?
Re: Question: How do I safety replace the CW shaft adapter (got it off, grease?)

Roland Christen
 

WoW, you have a generous neighbor to give you a mount for free. Stuck out tongue winking eye

Rolando

-----Original Message-----
From: Roger Howard <cargostick@...>
To: main@ap-gto.groups.io
Sent: Tue, Jun 1, 2021 8:39 pm
Subject: Re: [ap-gto] Question: How do I safety replace the CW shaft adapter (got it off, grease?)

1100GTO.  I got it free with the help of my neighbor, but just wanted to post that I used some lube on the insert to hopefully keep it from happening again.  Yes, I do have the insert.

--
Roland Christen
Astro-Physics
Re: Question: How do I safety replace the CW shaft adapter (got it off, grease?)

Roger Howard
 

1100GTO.  I got it free with the help of my neighbor, but just wanted to post that I used some lube on the insert to hopefully keep it from happening again.  Yes, I do have the insert.
Re: Will the Mach 2 support .....

Marcelo Figueroa
 

What!!!, you don't have an infinite number of telescopes, what kind of world is this where you can't have an infinite number of telescopes ??? :D
 
Great setup, we will be watching for the results. Here we are betting on the ASI 6200. These new cameras are ridiculously sensitive.
Re: VIDEO - Mach2 Right Ascension Belt Adjustment

Joseph Beyer
 

Interestingly the belt seems to be the astronomical mount equivalent as the drive belt on…Harley Davidsons.  Probably no relation.  The drive belts on the motorcycles have a service life of 60-100K miles.  My guess is the belt on the Mach2 lives in a much kinder environment and the life span will reflect it. 

On Jun 1, 2021, at 6:06 PM, M Hambrick <mhambrick563@...> wrote:

I am going off topic a little bit here, but many of us who started driving in the 1970's will remember the introduction of these toothed rubber timing belts in automobile engines. Prior to this the timing was always maintained with chain sprockets.

Belt driven engine timing got a really bad rap in the US, and deservedly so because the US carmakers chose to introduce this concept on the really cheap cars like the Chevy Vega, Ford pinto, etc. The life expectancy of these timing belts was supposed to be about 30,000 miles. I was working as an auto mechanic in those days, and our shop saw a lot of cars come in with engines that had to be almost completely rebuilt because the timing belts broke while the cars were going down the road at 55 mph.

In the late 1980's a new type of hydrogenated nitrile rubber was introduced onto the market that was designed for use in hot, oily environments, and most of the timing belts were converted over to this new polymer. I think that Kevlar also showed up at about the same time. Now, most timing belts will last at least 100,000 miles.

Mike

Re: VIDEO - Mach2 Right Ascension Belt Adjustment

M Hambrick
 

I am going off topic a little bit here, but many of us who started driving in the 1970's will remember the introduction of these toothed rubber timing belts in automobile engines. Prior to this the timing was always maintained with chain sprockets.

Belt driven engine timing got a really bad rap in the US, and deservedly so because the US carmakers chose to introduce this concept on the really cheap cars like the Chevy Vega, Ford pinto, etc. The life expectancy of these timing belts was supposed to be about 30,000 miles. I was working as an auto mechanic in those days, and our shop saw a lot of cars come in with engines that had to be almost completely rebuilt because the timing belts broke while the cars were going down the road at 55 mph.

In the late 1980's a new type of hydrogenated nitrile rubber was introduced onto the market that was designed for use in hot, oily environments, and most of the timing belts were converted over to this new polymer. I think that Kevlar also showed up at about the same time. Now, most timing belts will last at least 100,000 miles.

Mike
Re: Will the Mach 2 support .....

M Hambrick
 

Thanks for showing us this imaging setup Roland, and yes, please share your results including your guiding graphs.

Mike
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