First Light with new ASI585MC Pro.: Page 25

First Light with new ASI585MC Pro.

w7ay

Kevin_A I need a few good clear nights to retest my old Rokinon and see how it looks focussed to neutral and to retest for aberrations at that setting.

The 40mm Sigma is really well QA'ed.

After spending hours (more than one night) adjusting backfocus. What I eneded up is a backfocus that caused the line in the focus window to point precisly at the center of the infinity symbol!

I.e., the backfocus is at precisly where they have designed it.

The key for me is to first remove tilt, and only then tune backfocus. I could have save a lot of time if I had started doing that in the first place.

I had a set of larger (102" diameter) tilt plates made and it is heading my way right now. This next design will clear the entire cylinder of a 90mm ZWO camera, and will allow me to adjust tilt with a very long 2mm hex wrench from way back of the camera :-). It should make adjusting tilt and backfocus a breeze (like the two-plate-tilter allows you to adjust the tilt of an ASI2600 from the back). It is worth the money for the new tilt plates to prove this to myself. Paying money for knowledge is the most worthwhile thing one can do with money.

made by Samyang optics so maybe I will have better luck with their house brand than rebrand.

I'll bet they both go through the same fingers and hands at Samyang. I don't think they have different factory buildings for the two labels.

Every internal element that I have looked at are identical between two Samyang 135, and a Rikonon Cine. The only difference I have found so far is the number of brass shimming washers for the front lens group.

Even the three stupid small black screws are the same :-)

But... there is a different Rikonon 135/T2.2:

https://www.adorama.com/rkx135c.html

Much more mullah, and with huge lens hood -- 114mm. It touts close focusing -- if that was their design goal, it is a complete waste for astrophotography.

But (ha ha) it has 11 iris blades, so 22 pointed spikes.

Chen

Kevin_A

w7ay it is interesting that you said the Sigma focussed exactly at the centre of the infinity mark as that made me think about my Tamron. I just tested that lens again on my Nikon Z7 and it too focussed precisely at infinity right in the middle… but on my cooled camera with a filter was closer to the 3’ mark…. Hmmmm, i will have to recheck that as maybe the zwo sensor back spacing on my 183mc pro camera is off a bit or my stack was off. I tested with that low end camera due to the smaller pixel scale. I never have issues with getting rid of amp glow but holy noise cow!
I wonder why adding 0.62 for a 1.85mm thick filter would throw it off so much and I did get bad stars on the cooled and better on the Z7. I will recheck that too next clear night as I think something was amiss. It is amazing how other peoples comments opens up thoughts regarding one’s own projects and conquests. Thanks… haha

Kevin_A

w7ay zwo must have copied their ALT/Az implementation for their AM5 from the Skywatcher Star Adventurer… it takes me 15 minutes to get my PA dialed in with their coarse crappy large pitch adjusting knobs. My god my SA is actually better. It would have cost nothing to use a very fine pitch for PA adjustment….rush rush rush copy copy copy.

w7ay

Kevin_A it takes me 15 minutes to get my PA dialed in with their coarse crappy large pitch adjusting knobs.

I do not think the person who designed that has ever polar aligned a mount in his/her life.

Chen

Kevin_A

w7ay Emcam Astro has a new mount offering that has a nicer and finer PA implementation. Not sure if they are china brand but think so.

Kevin_A

Yes they have a few different models all made as you say probably on the same line. Even the Xeen is made there too. I see 3 other versions… manual 135 regular, DS cine and DSX cine versions…. All same internals, 2 de-clicked and one with weather sealing… except on Nikon version. I will try the Samyang version just for kicks and see.

w7ay

Kevin_A Not sure if they are china brand but think so.

Yes, Chinese company in Shanghai (so not that far from ZWO). Uses the same Chinese strain wave gears as the larger ZWO mount, but are much better mechanical engineered. My mom was born in Ningbo, across the river mouth from Shanghai :-).

But I think it is emcan astro.

https://emcanastro.com/about/

Have you noticed that none of these Chinese copycats can make a mount that weights as little, nor as compact, as the RST-135? They also have god awful hand controllers. The Hubo-i handcontroller for the RST-135:

https://www.ganymedes.nl/wp-content/uploads/2021/03/Hubo_i_for_RST-135_Manual_ENG_v1.0.pdf

The handcontroller manual alone is larger than the manual for the entire ZWO mount :-).

Chen

w7ay

Kevin_A E

By the way, Kevin, have you thought about spreading the payload of your ZWO mount sideways (e.g., using a side-by-side mounts, like I do with my dual saddle plate) instead of stacking stuff taller, and thus further away from the RA axis?

All the way back to the RST-135 (and perhaps even further back to Hobym), stain wave mounts have emphasized the need to keep the moment arm short. Emcan claims that they have designed their mount so the declination plate just 80mm away from the RA axis. I just measured my dual saddle plate, and it is 75mm away from the RA axis .

My dual saddle plate itself adds another 10mm (flexture? whats that?), and a PrimaLuce Losmandy dovetail clamp another 25mm or so).

The more I look at the Emcan mount, the uglier it is (although not as ugly and with gaudy colors as the ZWO mounts). Just compare to what the RST-135 and RST-135e look like. The Chinese mounts look like they were designed by Neanderthals. Years at Apple has taught me that well engineered stuff don't have to also be ugly.

Chen

Kevin_A

w7ay yes, Emcan… bad 1 finger typing on iPad. Haha.

Kevin_A

w7ay I have thought about side by side but remember I am using a AM5 mount… so would I really see any gains? Haha. It runs fine then not.. so it is not an issue with lower consistant RMS but rather an issue of inconsistancy… and that cannot be changed by a shorter moment but rather by a better set of gears! Haha my mount is like a gear that has a section where the teeth are missing on it…. Runs fine then crap hits the fan every 30 minutes for a few minutes, then fine again. But hey…. It has been better than my last 2 iOptron mounts that both needed over 6 different parts replaced each after 1 month of use. Even iOptron was surprised how bad they were. I still had to pay $300 each to ship to get them to fix. So…. For now I will take the 50 minutes of good images an hour from my crappy AM5 and shut up as I know it has been worse in the past. Nothing like ripping apart my iOptron mounts every other night and trying a few hundred things and still not get it to run under 2”rms even though I know how to set bearings perfectly and set a mesh fabulously… only to be frustrated night after night by badly machined and put together parts. Ok, rant over! Haha so I am good having a longer moment for now…. At least I am imaging this year and last year compared to 2 years of no good imaging.

w7ay

Kevin_A but on my cooled camera with a filter was closer to the 3’ mark…. Hmmmm, i will have to recheck that as maybe the zwo sensor back spacing on my 183mc pro camera is off a bit or my stack was off.

That is almost for sure wrong backfocus.

I just checked the Samyang 135 that I fooled with backfocus the other night -- the middle line of the depth of field scale points.... right at infinity mark.

When I get the larger tilt plates in, I am going to keep the EAF and focus right were it currently is, and start tuning the Askar backfocus adjuster for best focus with a Bahtinov mask.

Chen

w7ay

Kevin_A t runs fine then not..

One day, you too will stop buying mounts from China.

With mounts from Korea, Japan, Italy, Greece, why would you even get near a Chinese mount?

Would you buy a car from China? If not, why would you buy a mount from China?

At least get a Taiwan mount.

Rule #2: stay away from things that are shilled on YouTube. Have you ever seen a YouTube shill gush at a 10Micron or AstroPhysics mount, or an RST-135? Nope. And yet, there are plenty of those being used (just check Cloudy Nights).

Chen

Kevin_A

w7ay
You wrote….
I just checked the Samyang 135 that I fooled with backfocus the other night -- the middle line of the depth of field scale points.... right at infinity mark.
So…
Are you recording the actual measured stack thickness for reference with your lenses to see how it compares to spec plus filter diffraction compensation spec. I am not 100% confident in zwo spec for their camera BF spec. I opened up a guide camera the other week and noticed that their sensors are not exactly as specified as sometimes they fold a ribbon cable under the circuit board and other times a double fold and it just relies on 2 tiny screws to hold it roughly in place. I found that weird and non engineered! As far as the eaf… yes, i would need to drill and tap it as you show!

Kevin_A

w7ay yes, I will have my eye out for a non china mount in the future. It is nice that SWG mounts are going more mainstream and I think there will be better offerings going forward. Truth be told… after 2 years of using bad mounts I almost packed it in and the with the AM5 I was still on the fence as it was not better by much. Imagine buying 3 bad mounts in a row…. Wow! Is that a curse or what! Haha
But, playing around and testing keeps me happy and I survived telling myself it was a good learning curve. Once I fixed them both due to their bad machining I sold them both. Regarding a lower moment, I may turn my Askar FRA300 setup sideways as it is very tall for its size… too much holder and handle! I might drill it out and mount the guidescope sideways on the dovetail upright or similar. Another project for another day or just use 2 crossed losmandy plates or similar.

w7ay

Kevin_A I may turn my Askar FRA300 setup sideways as it is very tall for its size… too much holder and handle!

You can get it closer to the declination plate by losing that big red clamshell too. These "tube bands" look familiar? :-)

But you also have a ZWO problem. That EAF is sticking below the declination plate. That prevents you rfrom mounting on a dual saddle plate. I solved it by mount the EAF this way:

Chen

Kevin_A

w7ay i am fairly confident that a lot of manufacturers comment on the moment distance to the masses that want to use a C14 or C11 on their mounts! Not sure if a 3kg 60mm scope would affect a good SWG mount in regards to being 2” closer to the axis. Maybe help in regards to gear flexture slightly when hanging sideways…. Not sure 3-10kg would do any harm or do worse. But rhats just me thinking out loud.

Kevin_A

w7ay i am still trying to figure out which scope you took those tube rings off of… not the WO 68… hmmmmm, not sure what rings are 82mm ones.

w7ay

Kevin_A i would need to drill and tap it as you show!

I had used M4, but I think M3 might be better -- what I will be using with the EAF going forwards.

The weakest link is not that plate interface, but the backlash from the cheap crap gears in the EAF's stepper motor.

Are you recording the actual measured stack thickness for reference with your lenses to see how it compares to spec plus filter diffraction compensation spec.

Yes. Everything appears normal.

In the old days, I remember ZWO claiming +/- 0.5mm for the flange focal distance of their cameras. So far it looks better than that, if you can believe.

I found that weird and non engineered!

If ZWO were in the US, I would call their work "redneck engineering." They really need to hire university educated kids who had been doing astronomy as a hobby.

Chen

w7ay

Kevin_A i am still trying to figure out which scope you took those tube rings off of…

ZWO camera ring:-).

Chen

Kevin_A

w7ay thats what I initially thought but a 90? Shim or is a 78 oversize?

w7ay

Kevin_A thats what I initially thought but a 90? Shim or is a 78 oversize?

A layer and a half of cork sheet on a 86mm diameter ring, i think.

BTW, these rings from Japan are pretty good. I use the 95mm one on my Baby Q:

https://astrohutech.store/product-category/b3-more-blue/mounting-rings-b3-more-blue/

I had originally used PrimaLuce rings that I bought together with the FSQ, but got rid of them because of the gaudy color. Will never touch PrimaLuce rings again.

Chen

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