JamesAstro2002

Thanks for the input. 

The thing is, I paid a decent chunk of change to get this triplet and I was hoping to get better results with it. My old bargain basement 200pds at this point is giving better results than something 3 times the cost. Also, I have plans for mosaics, so ideally, I'd need the stars at the corners to be somewhat better.

The previous owner of the scope was using a similar configuration as mine and had perfect stars all across the frame, so I know an improvement is possible.

Hi there, 

I've recently obtained an 80mm EDT Pro Altair refractor and am getting some star elongation in 3 corners. I have adjusted backfocus to be around the 55mm mark, using a mix of spacers and T2 delrin rings. The center and top left look to be perfectly round. The other 3 corners are elongated all in the same direction, as opposed to the normal radial pattern seen when the sensor is too close to the field flattener. The top right perhaps seems to be the worst.

I'm wondering whether this is a mix of tilt and backfocus? Wasn't sure if it would be sensor tilt on my 1600mm pro, as before getting this scope I was using a 200pds and managed to get perfectly round stars across all corners, which would make it seem to me the sensor is not an issue.

I've attached some images below from aberration inspections.

If anyone has some input, would be really appreciated!

9 minutes ago, david_taurus83 said:

Hi James,

Any chance you can stretch and convert to jpegs and post directly to the forum?

Done

Hi,

Recently I've been able to get out under the stars and test my new Altair 102 triplet - however, I've noticed some odd star elongation and it's really got me stumped as to what's causing it.

https://drive.google.com/open?id=1rze_Lwnlm4LBiV2mer5gnLEQ2pKaRain  

This was the first test frame I was able to gather a couple nights ago. As you can see the stars are evenly stretched across the frame, going in the same direction.

https://drive.google.com/open?id=1BAE7u88qT0PBkm2jBS1atBiV8WVMftx9

This was the first frame I got from last night, and the stars looked a lot better. All I did was swap out the two 1mm baader derlin spacers I was using for just a single 1.6mm one, thinking the two stacked together might have been causing tilt or something. But later in the night have taken that initial sub I noticed the streaks came back again! I was looking at the same target, just a little later in the night and it occured again. Here's another frame of pinwheel to show it does it even towards the zenith.

https://drive.google.com/open?id=1kmJ9eN-d6PIeLPJ-G4pounnHZoCTjrdh

I'v ruled out tracking and guiding issues, as I can see the elongation even in a 1 second exposure, just as much as in a 3 minute exposure. Any ideas? It's got me stumped. Seeing that the stars were OK at the start of the night, could it be something to do with the scope getting cooler and the metal contracting? I'm not using any dew heaters.

Edit: Added stretched files:

Cheers,

James.

Hi,

I've been messing around trying to get the spacing correct between my TS photoline 0.79x corrector and 1600mm, now that it's better I have noticed some tilt. It seems the stars are good in the top left corner and the central part of the frame, but all the other corners not so much. How does one go about adjusting tilt? I've also attached my imaging train - I'm using some push fit adapters, could that be causing it? Or do I just need to adjust the spacing very slightly to negate the tilt?

And yes I have a dovetail bar zip tied onto the finderscope bracket, don't judge me it was for balancing, 😂

The second set of screws, closest to the end of the tube.

Yeah, I was quite suprised at how large they are! I managed to get hold of William Optics and they instructed me to loosen the lens cell screws by an 1/8 turn. I did so and tested it last night, seems to have sorted it I think! The conditions were terrible, so only managed to grab some quick tests before it clouded completely.

http://www.opticstar.com/Run/Astronomy/Astro-Telescopes-Ascension.asp?p=0_10_1_6_30

Hi all,

I found a good looking deal for one of these telescopes second hand. Was just wondering if anyone has had any experience with them or know about them.

Cheers,

James.

Yeah, I'll get in contact with them. Thank you.

Okay, thanks - that makes sense. Yes, I have a dew heater on at all times and always see these effects.

Hi all,

Apologies if this has been asked before, but I've come to notice these odd artifacts on stars with the William Optics Z73. It almost looks like something's protruding into the light path?

Come to think of it, the stars do look rather bloated and quite large - is this just inherent being that it's a doublet? This was my first hack at LRGB.

Cheers,

James.

Great, thank you both. I am leaning towards the baader, but of course SW is still an option. And thank you for the offer @Spaced Out - I'm sure I'll ask more questions if I buy it, lol.

7 minutes ago, Stub Mandrel said:

Lots of us! It's a match made in heaven

Awesome! That picture looks mighty fine 😀

3 minutes ago, Spaced Out said:

I use a Baader MPCC mkIII.

Cool. As @Stub Mandrel just said I probably will just have to buy a CC again, I've realised just how bad the coma is without one. Did you require any extra spacers to get the right backfocus? Would you mind sending a picture of it?

Awesome! Thanks for the reply. What Coma Corrector do you use out of question?

Hi all,

I've been thinking about cracking my 130pds out again for imaging with my asi 1600mm. Any other users of the 1600mm and this scope?

And would an adapter like this be okay for connecting the cam? I want to test the scope out before purchasing a CC again.

https://www.firstlightoptics.com/adapters/astro-essentials-2-inch-t-mount-camera-nosepiece-adapter.html

I never thought about filter sizes, thanks for bringing that up. I also came across the QHY 163m variant. Does this have the same, larger backfocus requirement?

Nice, that's quite a range of different cameras! I'll try find some reviews on the Altair versions. If not, I'll probably go for the ZWO considering its great reputation.

58 minutes ago, Adam J said:

Look up micro lens diffraction pattern for the ASI1600mm pro before you make your final choice. However, don't agonise too much as either one will provide good results. 

Adam

Cheers Adam. I'm looking at the Altair astro 183m now. It's a little cheaper than the zwo and comes with a nice case. Seems all the same to me, are there any caveats you know of with the Altair counterparts? 

Okay, thank you. That's nice for just one hour!

Hi,

I'm considering taking my first step into the money pit of mono imaging, but I'm stuck between two options. The 183mm or the 1600mm. Currently I'm using a William Optics Z73. The 183mm is more appealing to me at the moment because of the price, I could buy it along with the filters and it would still cost less than the 1600mm alone. I like the FoV of the 183mm as well, as most objects fill the view with that sensor and my scope. But I heard somewhere that the 1600mm is more sensitive? Or Less noisy, can't remeber. Either way, is the 1600mm going to be that much better or not? Or is it just down to the size of the sensor?

Also, what models are best for either of these cameras? Considering the ZWO, QHY and Altair options I wouldn't know what's better. Or is it just down to price and availability?

Okay. Thanks for the input everyone! I'll try looking into the Omegon scope more, but I'm leaning towards WO. As @blinky said, at least I know what i'm getting. 

Hi everyone,

I'm in the market for a new apochromatic refractor for widefield imaging. At the moment i'm set on the William Optics Z73, but then came across this: https://www.astroshop.eu/telescopes/omegon-apochromatic-refractor-pro-apo-ap-71-450-quadruplet-ota/p,60855. I've not heard of this brand before, does anyone here own this telescope or know about it? Price point looks great for what it is though. Any other recommendations for a widefield refractor to take into consideration? 

Cheers and clear skies,

James. 

14 minutes ago, Adam J said:

The next thing you will want ot do it to chop down that focuser tube to stop it heading into the light path!

Yeah, I've done that already, looks like I'll need a few more mm off then, thanks for the heads up!

3 hours ago, alacant said:

Hi. The cc causes reflections. Cheap way out: don't include bright stars in your fov or just heal it away. To lose it completely and keep your stars into the corners you'll need the other sw cc. It would also focus further out and in so doing obviate the need for the hacksaw.

Oh right, okay that makes sense.

4 hours ago, alacant said:

Cheers and well done for sticking at it:)

Thanks again for the help! Clear skies