SAW

On 28/06/2023 at 10:19, Phillyo said:

Does the little Redcat 51 tick the box for you? That's 250mm focal length so might be too wide for what you're looking for?

Phil

Yep ended up getting one of these. Hopefully test it tonight 🤞

Hi,

I'm looking for a decent quality scope purely for imaging to use with my 2600MM. Currently have it mounted on my Stellamira 90mm triplet but may sell this. Ideally I would like something that doesn't require a reducer/flattener so all I need to mess with is tilt ! Narrowed my choices down to Askar FRA300, Askar FMA230 (I know this has a reducer), Sharpstar 61 (not sure what the differences are in the mark 2 and 3 ?)

Thanks.

This is what I am getting now with the 1.6mm of spacing removed. Off-axis aberration has dropped quite a bit but looks like I still need to be a bit closer, tilt is still way off !

I've removed 1.6mm of spacing i'll give that a try and compare the Off-axis aberration before I tackle the tilt.

Just now, Gary Clayton said:

It's impossible for me to say as I don't have access to your rig, it's going to be trial and error on your part. Does you camera have a tilt adapter ?, if so your need to work out which side is which as well as it's top and bottom, if your using a ZWO camera my understanding is that the bump in the camera's body is the top, have a look at these videos to get you started.  https://www.asgastronomy.com/collimation-tilt-and-backfocus/

I don't have the tilt plate connected the camera is bolted directly to the filter wheel.

I have some tilt shims which side do I need to put the raised part on ? How much should I reduce my spacing each time to notice any changes ?

I loaded this frame into astap.

Light_Cygnus_300.0s_Bin1_H_20230624-012407_0031_a_REF.xisf

Ok will do when I get home. 

13 minutes ago, Gary Clayton said:

Hopefully this guide should help

Would that cause the stars to look like crosses if it's too close ?

Thanks all. I'll check a single sub.

12 minutes ago, Anthonyexmouth said:

Looking at the top of the frame it looks like it was knocked or lost guiding. Is that a single sub? Exposure time?

That's a stack of 48x300s. 

I was using my 2600MM last night on the 90mm for the first time, normally use the 183MM without any problems. What is causing the really bad star shapes all along the bottom ? Can I fix it or do the optics need collimating ?

I think the 200PDS will be the safest choice.

Hi,

I want something with a long'ish focal length for galaxy imaging. I'll be using a 183MM and it will be mounted on GEM45 I'm not sure which of the above scopes to go for ? My current imaging set up, Stellamira 90mm with 2600MM, filter wheel etc etc weighs 8kg and the mount is fine with it. Is the 250PDS and Quattro going to be too much for the Gem45 ?

Thanks.

On 12/06/2023 at 10:39, aleixandrus said:

 These corners make me VERY jealous, @Adreneline 😁

@SAW: I think it depends on the direction of the elongation... If the stars are elongated towards the edge, you are probably too close so you can add some shims in that corner. However, if the elongation is perpendicular to the corner-to-center direction, you are too far away... which is more difficult to address as you need to 'subtract' distance and you will mess up the other corners. If they have a good shape, maybe you can live with one ugly corner. Do you have some pic to show?

Here is a single 120s image all I have done is a EZ Soft Stretch in Pix.

Out of interest what cameras are people using with the Samyang ?

I'm thinking of buying another one but this time a OSC, normally use mono.

I've got my focus correct now so it's at the base of the L mark but the stars in the top left and right are slightly elongated. I have some tilt shims 01, 0.2 & 0.3mm, do I need to shim the top where the stars are elongated or the opposite side ?

I'm almost there 😀 need some of those 0.1mm shims now. The white marks are where I've been getting focus using different shims. 

1 minute ago, Adreneline said:

I'm not sure why you are not following the advice I gave you on the 28th May; you need to make incremental changes of 0.1 mm not 1 mm. 

Where do I get 0.1 shims ? Smallest I have is 0.5mm.

Just redoing the spacing on my set up.

I have the Samyang Lens to M48 adaptor, so from this I need 44mm spacing to the sensor ?

I have the 2600 with the tilt plate removed so that mean the sensor is 12.5mm back from the camera face ?

I then have a filter wheel, 20mm.

Which means including the M48 to M42 adaptor https://www.firstlightoptics.com/adapters/astro-essentials-m48-to-m42-t2-adapter.html i should need about 11.5mm of spacing ?

Is that correct ?

Last night I just experimented with trying to get the correct focus postion with my 2600MM so it would focus in the same postion as it did with the 600D. With the correct spacing it would focus way past the bottom of the L mark, even just adding 1mm of spacing then through the focus back the other way where it was in focus before the L mark.

It's a pain trying to get it adjusted as I am using the Astrodymium mount so I have to strip eveything off just to adjust the spacing !

Wondering if I could try it in the daytime on something far away ?

Going to give it one more try then I'll be changing it to a small wide refractor.

This is where my focus point is using the 600D and Samyang according to my ASI Air Plus, is this where I need my focus to be correctly spaced when using my 2600MM ?

Used my 600D with the Samyang last night. Just a few 10s subs stacked of M86, no flats hence the vignetting. Stars are still poor in the corners. Was at f/2.8/

2 minutes ago, bottletopburly said:

No corrector required for MN, though both need a decent focuser I know someone on the east midlands forum that just upgraded the focuser body (AliExpress I think )only on his and turned out a decent focuser good stars 

I'll be using my ZWO EAF on it.

Looking to use one of the above with my 183MM. Any advantages using the 190MN compared to the 200PDS ? Both give me the same FOV, would need to buy the coma corrector for the 250. I have owned the 130PDS before.

Thanks.