Jay6879

On 20/02/2023 at 03:33, rl said:

I have owned several small apo doublet / triplet scopes in the 60mm - 90mm range and my example has the best optics for the aperture of any of them.

Quibbles; The OTA is not the lightest and some people complained of slightly wobbly focusers (early versions only?). The tensions are adjustable, and I haven't hears of this for a while now.

It's been around a long time in various incarnations. WO have a habit of changing the model with the weather (it's called continuous improvement..) so the fact that the GT81 has lasted this long with the optics unchanged probably says something about the commercial benefits of keeping it in production. I paid £450 for my MK1 secondhand ant it's a keeper. 

This is good to hear! I ended up getting the gt81, it's a newer model that has the rotator built in. Unfortunately it looks like weeks of clouds ahead so Im not sure when I'll get to try it out!

On 20/02/2023 at 04:51, Elp said:

No GT here, but have owned a z61 for a number of years, optics are super sharp for everything I've put it through (planetary, deep sky, ha solar), visual and photographic, so it speaks for itself.

I also had a Zenithstar 61, fantastic scope that set me down the path of William Optics ownership. They make fantastic scopes. After that came the Zenithstar 81, and now I have the GT81. I just wish there was a 1x flattener for it!

12 minutes ago, scotty38 said:

I have one and think it's great although it's my first, and only, astro scope so cannot compare with anything else personally.

One of my last images before clouds etc rolled in:

Wow that's a stunning image! Nice stars, don't see any chromatic abberation, good detail on the galaxy. Ok this looks promising! Too bad William Optics doesn't make a 1x flattener for it.

Im looking at picking up a GT81 specifically for astrophotography. Looking for any impressions or opinions from people with experience?

How doy ou like it? Is it a worthy upgrade over a doublet?

11 hours ago, ollypenrice said:

Negligible CA. I would never have given it a thought.

However, on my monitor (which is calibrated) I see no green caste but I do see that your blues tend towards magenta, suggesting too little green weighting. Look at the bright star half way down on the right. I had a play with a screen grab in Photoshop and tried to lose the magenta dominance in blue. I also tried to bring out the blue in the Iris and open up the colour in the dust. Basically this meant a lift in the lower brightness reds. I felt that, above the fainter signal, you did have a green deficit.

Olly

 

Could that have happened from being a bit heavy handed on the scnr?

7 hours ago, geeklee said:

Really nice image - how long was the integration?  From the UK?

I see a little CA.  The only person that matters whether its acceptable... is you   You could do a little with it in processing but it doesn't detract much from the image - I was enjoying the Iris and dust .  

It looks pushed hard viewed at 100% and there's maybe a slight green cast across the image if you're looking at it again in processing. The latter easy to fix if you wanted.

Thanks for sharing  Hopefully you're pleased with the image, you should be!

I'm in Canada, and the integration was around 15hrs. I'd love to see what would be revealed by doubling that time! I'm still quote new to Pixinsight, only been using it for a few months now but i had posted the image during a "debate" on well corrected doublets (of which the Z81 would be considered one) and when I posted that pic the people on the uh...other side of the debate told me it was full of CA which I found bizarre haha.

This was my first go at processing this object beginning to end and I'm definitely going to have another go at it and carry forward what I've learned. I'll certainly consider not pushing it so hard, and correcting the color!

I appreciate all the responses!

I'm curious to see if others see any chromatic abberation, and if so would you consider it acceptable?

I got thjs image using an asi533mc and a Zenithstar 81.

20 hours ago, ONIKKINEN said:

Love his sense of humor. This one clicked with me, something with the upbeat music and whats happening on screen makes it so funny:

 

Haha I've never seen this one. You're right l, the jaunty music makes it. Some of the text killed me too. 

"Reslly get in there"

"Egg whites contain a natural cleaning solvent"

Edit - and him trying and failing to hang it off the clothesline 🤣

All I know is astronomy tends to be so...dry. There doesn't seem to be much humor or joking around (my numerous funny posts on cloudy nights with sweet gifs and stuff that wre constsntly being deleted is good proof) so when i stumed across this video this dude instsntly gained a subscriber..

My asi585mc just got delivered today coincidentally. I'll be using mine as a guide camera/planetary camera since I have a 533mc for dso stuff.

The skies are actually clear tonight so I kinda want to try imaging Saturn and Jupiter with my Skymax 150. I'm also interested in doing a mosaic of the moon using the same Skymax 150. Judging by what astronomytools shows it'll be at least three panels which will be ridiculously high res.

12 hours ago, newbie alert said:

Depends if you're using the flat61A

The spec says 67.9mm if you are

 

Yes it's a flat61A. He is a screenshot from tonight after adding the other 21mm spacer..

And a link to the raw sub..

https://drive.google.com/file/d/1aztjkp9c_haXMsfYKMmv5UZW8yqVm2xV/view?usp=drivesdk

Stars look way better! 

1 hour ago, newbie alert said:

Don't forget to include the 6.5mm backspace ( camera body to sensor) within the spacing distance 

Wait...no hold on. The camera already comes with an 11mm spacer threaded on. So the math would be..

21mm+16.5mm+11mm+6.5mm(camera body to sensor)=55mm

ZWO says to set the flattener at 12.9mm for dslr's, a dslr also requires 55mm of backfocus. So essentially I just need to add that other 21mm spacer (which I wasn't using before, only the 16.5mm and 11mm spacers) and I should be fine....right?

1 hour ago, newbie alert said:

Don't forget to include the 6.5mm backspace ( camera body to sensor) within the spacing distance 

21mm spacer+16.5mm spacer+6.5mm camera body to sensor gets me to 44mm.

67.9mm-44mm=23.9mm

So my flattener should be set to 23.9mm? Am I doing this math correctly?

1 hour ago, newbie alert said:

Zenithstar_61_Owner_Manual (1).pdf 3.21 MB · 2 downloads

Ah ok this is good info.  The asi533 comes with a 16.5mm and 21mm spacer, and a few really thin spacers. I'll have to figure out the math to see if I need more spacers or not. Or maybe the adjustment on the flattener will provide enough that those two spacers will be good enough.

14 minutes ago, vlaiv said:

Blow bulb, but really you want to take flats as flats sort out issues with dust (and other things like uneven sensor response if there is any).

 

Oh yeah for sure, flats are always used. I'll look into a more heavy duty bulb, like a Rocket Blower.

5 minutes ago, newbie alert said:

What scope are you using?

Zenithstar 61

5 minutes ago, vlaiv said:

Yes, it is dust - but rather far away from sensor.

Closer dust is to sensor "more concentrated" shadow is, and opposite happens when dust is further away - fainter and larger shadow becomes.

Ok, so the dust is more likely to be on the flattener optics or further down at the end of the refractor then? Any tips on getting rid of stubborn dust? I've got one of those lens bulb things but it doesn't do much.

30 minutes ago, newbie alert said:

Look like you need more spacing

Ayy, the top image looks quite similar to mine. Ok, this is encouraging! I only used one of the spacers that came with the camera (16.5mm), I'll try attaching the other one that came with it (21mm iirc).

25 minutes ago, VectorQuantity said:

This may possibly give some indication

https://astronomy.tools/calculators/dust_reflection_calculator

 

I use astronomy tools all the time and never knew of this tool, I'm on mobile right now so it won't let me click and drag around the circles but I'm going to give this a go first chance I get.

17 minutes ago, Ibbo! said:

They look like dust bunnies close to sensor, do you have flats ? If so they should confirm.

Geez, I literally took the camera out of the box, threaded in a 1.25" ircut filter and put it on the telescope! Though I guess it wouldn't take much for dust to hit the protective window on the sensor, even in that small amount of time. And no I don't have flats, by the time I got everything set up clouds rolled in. These were just some 5 minutes exposures taken on the preview screen of the asiair plus, then I just took a screenshot of them with my phone.

The point of that test exposure was to see how far I could push my new belt modded heq5-pro, and the jury is still out on that until I can fix these spacing issues!

Thanks for the quick replies, all is not lost! I dropped a decent chunk of change on the camera and got pretty freaked out by these issues, I never had anything with my t3i. Just pop it on and go.

First shots from my new 533mc. 300s preview exposure (beyond the star elongation at the bottom suggesting wrong backspacing?) what could these dark spots be? The weird thing is they weren't visible with a 5s exposure?

They don't look quite like dust motes? And what is happening on the bottom half of the image? The stars are radiating away from the center of the image. Its happening at the top as well but not quite as bad. Is this a spacing issue? This was taken on a Zenithstar 61 with the 1.0x adjustable field flattener.

Any help would be appreciated, this was my first night out in MONTHS. It took me awhile to aquire this camera and when the first test images came in I got pretty dejected with the results!

On 01/04/2022 at 06:17, vlaiv said:

Don't think you need x2 barlow.

Start without it.

That scope is F/13 and by the formula I gave above, as ASI224 has 3.75um pixel size, ideal F/ratio is 3.75 * 4 = F/15. You are already at F/13 and would thus need 15/13 =  ~x1.153 barlow. Using x2 barlow will put you at about F/26 - that is much further away from F/15 than F/13 is.

Even using x1.3 barlow will put you at F/16.9 - which is still too much and it would be better to just use F/13 as is.

You were correct, at least for the lunar images. The asi224 with the Apex 102 is REALLY zoomed in. I tried my hand and creating a mosaic for the first time and it somewhat worked out..I had massive stacking artifacts on one panel that ruined the full image so I had to crop it and was left with this..

I also purchased a used (mint condition!) 2x Celestron Ultima SV barlow for thr planets later on in the season. Thanks again for the help!

5 hours ago, vlaiv said:

Don't think you need x2 barlow.

Start without it.

That scope is F/13 and by the formula I gave above, as ASI224 has 3.75um pixel size, ideal F/ratio is 3.75 * 4 = F/15. You are already at F/13 and would thus need 15/13 =  ~x1.153 barlow. Using x2 barlow will put you at about F/26 - that is much further away from F/15 than F/13 is.

Even using x1.3 barlow will put you at F/16.9 - which is still too much and it would be better to just use F/13 as is.

Ah ok, I was hoping to get the images a little bigger with the bsrlow. What are the benefits of imaging at f/13 over f/26? Will it be not as sharp at f/26?

On 15/03/2022 at 16:59, vlaiv said:

@Jay6879

I see that you are confused

Here is simple equation

F/ratio = 2 * pixel_size / wavelength

Where wavelength and pixel size are in same units - say micrometers. For wavelength you should put 0.5um (which is the same as 500nm - wavelength of green light), unless you have reason to use other value. If you do that - equation simplifies to

F/ratio = pixel_size * 4

Welp....I completely bailed on everything I talked about in this thread. Instead I bought a wicked cheap used Orion Apex 102, an asi224mc and an ir cut filter. Just need a 2x barlow and I'm ready to rock! 

20 minutes ago, vlaiv said:

Very nice images!

You were right to stack barlows (although just using x3 at increased distance would have done the trick). NexImage burst has 3.75um pixel size and ideal F/ratio is F/15.

Starblast is F/4 telescope and it needs at least x4 amplification to get close to F/15.

Maybe for planets, but lunar does not have much color so you'll be fine with mono. You can also experiment with filters if you have any. Narrow band filters suppress seeing effects and are beneficial for lunar.

Link I posted is to a thread here on SGL where I originally posted the image with all the capture detail.

It opens fine for me - both the SGL thread and also the image posted on that thread. Not sure why you can't see it.

Here is the image uploaded again here:

Do right click / open in new window so you can zoom in fully to see the detail.

Wow! That's crisp. Tons of detail. Alright you guys have essentially pushed me over the edge here, I think I'll pick it up. He's selling it for less than half the cost new, I'd like a larger aperture but for the price it seems like it can't be best. Later on down the line I'll upgrade. 

What equation are you using to determine the best f ratio for pixel size?

4 minutes ago, Alien 13 said:

I have the C90 and a Z71 and would say that the Mak produces better Lunar images, the Mak also has the benefit of a far more sturdy camera mount.

I still haven't worked out if its best to attach the camera direct or use a 2 inch extension which compensates for the removal of the visual diagonal but it focuses fine both ways although the f/l changes a little.

My first ever image with the Mak, single shot with DSLR.

Alan

Wow that looks amazing considering it's a single shot! I can only imagine what could be produced with lucky imaging.

27 minutes ago, vlaiv said:

That really depends on pixel size, but most likely - you won't need a barlow.

If you image with Zenith star, do you possibly guide? And if so, with what guide camera?

Guide camera is much better option for lunar / planetary imaging.

C90 is a bit shy of being F/14 scope (F/13.89) and that is very well suited for ~3.45um pixel size. So any camera with say 3.3 to 3.75 micrometer pixel size can be used without barlow on C90.

If your DSLR has for example 4.3 - it would need F/17.2 and that means x1.23 barlow - not really feasible thing (you can get x1.5 barlow element and try reducing sensor / barlow distance to get to x1.23).

In any case - look up lucky imaging technique.

This lunar image was taken with 100mm Maksutov telescope (so just 10mm larger aperture than c90, but practically the same focal length):

 

Yes I do guide with the zenithstar using an asi 120mm-mini. It's only black and white though, that would be kinda lame for planetary imaging no? As for lucky imaging two years ago I started this whole astronomy thing with a tabletop Starblast 4.5. Despite the objections from people over at cloudynights I stacked a 2x and a 3x barlow on top of each other then a neximage burst and got these images..

Completely unconventional sure but hey these images blew me away! They were a ton of work, line everything up in sharpcap, hit record for ten seconds or so until it crossed the frame. Move the scope and reorient the planet, hit record for ten seconds or so rinse repeat until I had 5 minutes or so worth of data. It was immensely rewarding though.

So I have a basic understanding of lucky imaging, the processing I could use some more practice with though. This will be the first maksutov ive encountered so that's why I had these questions. Unfamiliar territory! I ousted that little starblast way outside it's comfort zone, was just curious where the edge of thay comfort zone lies with the c90.

I appreciate you taking the time to reply, you've always been helpful! Also the link yubposted has no image? It looks like the link is broken?

Thanks for the replies, everything sounds good then. Zenithstar remains my wide field imaging scope, the c90 will become my lunar (and possibly some planetary?) scope.

16 minutes ago, Craney said:

or.... look on ASTROBIN.

Plug in the type of scope on the search panel and you should get lots of images (albeit with a range of cameras as well).   Some will be Lunar.

I can speak highly of the C90.   It did give very crisp views of the Moon and was of the right FL to get a full disc with a DSLR.    ( very useful for eclipses ).

Good to hear that the c90 is a good little scope! And it plays well with a dslr? Just screw it into the t2 built into the rear and you're good to go?

If I wanted to use a barlow with the dslr how would I go about that? And what would be the max barlow I should attempt for imaging do you think? 3x?

I have a Zenithstar 61ii and have used to to take a few images of nebula/andromeda etc but recently came across a great deal on a Celestron C90, he seems like a really cool dude and is selling it for $200 (new is almost $400cad). I'd use the C90 for planetary and lunar viewing but I'm mainly curious to know if the C90 would produce a better lunar image than the Zenithstar?

I'd be using a t3i for now until I get a dedicated camera. Obviously the C90 would produce better images of the planets due to focal length but I'm not sure how to compare quality between scopes. Resolution? How is optical quality quantified? 

I'd appreciate any information on this, don't want to miss out on this sweet deal but would prefer to know if it's worth the purchase.