Backyardscope

Ideally before you invest in another telescope. All is not lost and certainly cheaper then buying another.

You need to find a astro retailer/optical engineer who has an optical bench, they would have the expertise  to correct the pinching on the lens and correct any astigimitism which maybe apparent. In newtonians this fix you can do yourself, unless there is something physically wrong with mirrors.

Re the flattener, I always try to obtain the matching reducer/flattener for the scope.

When removing the retaining ring of the flattener there is a slot on each side of the ring. You need something like a metal plate which rests inside both slits (but clear of touching the optical elements) of the ring and twist, but remember the lenses inside the flattener fit inside a certain orientation, so take care when assembling or disassembling if you take this route?

I would tackle fixing the scope 1st before dealing with the flattener issue.

Typically Far Eastern telescopes are manufactured in assembly lines where temperatures are usually warmer then colder climates which when they are used. The screws inside the lenses are usually screwed in tighter. They may check the lenses on some sort of optical jig, as part of QC.

Funny enough, the only manufacturer I have experienced which I have not experienced pinched optics is Sky-Watcher. I am sure there are some examples, but only small percentage. 

Once the telescope is corrected, try without flattener again. Then deal with the latter.

Apologies, yes looking at the image on a big screen, the stars look ok'ish, on the brightest stars you see the reflection of the spacers. If you zoom into the brightest star, you can actually the star being round and there is a ever slight pinching.

Triplets are much more prone to curvature then doublets, I agree with @Stuart1971 if the stars are not round in the centre of the image it minuses the issue of spacing regarding the flattener.

Did you need to have a dew band on while using the scope while imaging? what was the temperature outside?

It does look like a case of pinched optics. Another thing to check which is often ignored, is the retaining ring in the flattener , the one which rests on the optics. Is it screwed on ok, not loose or anything? 

You could just try imaging without the flattener to see how the centre stars look.

Interesting article about Honders Optics:

Honders camera and telescope (telescope-optics.net)

The only way to learn is to tinker, tinker and tinker, and when you still can't get it right, have a rest, then tinker more. I often wonder about getting an RC for smaller object DSO imaging. That's one scope I have not tried yet!

Even so, a good image you have there, may I say.

On 22/04/2024 at 19:55, tomato said:

Any sign of the Skywatcher HAC125 at the show?

Looks like an interesting scope for Astrophotography, optics designed by Lichtenknecker Optics, same company which designed the optics of the Esprit's and Evolux 62ED.

On 24/04/2020 at 09:21, FLO said:

Officially the telescope doesn’t exist, though Synta are clearly beta testing one (perhaps the Austrian retailer knows one of the beta testers). It is not clear yet if it will come to market. 

HTH, 

Steve 

Why would they advertise it as Pre-Order?

I am waiting for a Skywatcher MN150 to be released, the Quattro 150P, brilliant scope but just a stop gap for now.

Have you checked the clips on the primary mirror to make sure the mirror is not pinching.

They should be just touching the mirror, not forced down and also they should he enough that you can easily rotate the mirror within the clips.

Apparently, the banding issues have now been resolved with the latest firmware according to SVBony. I initially had this model, but had to return it back for the banding issue.

I replaced it with a SV405CC, very much the same as the ZWO ASI294MC Pro without the USB Hub. Very nice performing camera as well.

The Nebula really comes out nice, even though you have used a scope at f/7.6, the 100ED Doublet so under rated for DSO Imaging. You have encouraged me to invest in a reducer for my C100ED, 

A 100mm Doublet, very versatile scope.

Mark the tube and primary mirror cell position. Make a circle paper template for the primary circumference, fold it to get centre point and place that gently over the primary mirror, then you will get a pretty accurate idea where is centre point.

You can get a cotton bud, slightly dip it with water (some use nail polish remover) and dip the bud on the centre spot and slowly remove it. Use a corner of soft tissue,  lightly touch the corner to soak up any bubbles up left on the mirror.

Buy a Cats Eye centre spot and using the Cats Eye template stick the centre spot onto the mirror.

Check that the focuser and secondary are all aligned, then re-collimate, then Star test.

Testing and Patience is the key!

StellarMate OS 1.8.1 supports RPi5

The primary has been pushed up the tube a bit, so you can achieve focus with a CC and camera.

I can't remember if the secondary size has changed?

I forgot to ask, was you using a coma corrector as well, generally the centred the object would be round, even without a corrector and the coma would be further as you go out of field.

The secondary collimation screws should be tight and also check the secondary spider is not loose the secondary screws are good and before i forget again the spring tightness on the secondary holder and on the primary collimation knobs.

Is the object centred in your fov? if so - the collimation is out, also you might want to check the retaining clips on the mirror. The clips should be just resting on the mirror, then forced down or tight. You will find astigmatism will be apparent.

When dealing with F4 Reflectors, mechanics, optical parts must be all aligned best as possible.

Don't rely on cheap lasers to collimate fast scopes.

A 2" sight tube for the secondary and a Chesire eyepiece for the primary.

PS. If you get fed up with scope, ping me a PM about the scope, thanks.

Demand you want a telescope replacement.

I was in Bortle 8, but now in Bortle 3-4 

I echo recommendations of a Skywatcher 100ED, Celestron 100ED in any other guise.

The starfield 102ED comes to mind as well.

The spider was called James Web.

Thanks, One of on my list to do. 

Warm room. with telescope automation.

I have seen metal rings without the adjusters on a European astro dealers website, I think its probably easy just to print off something. Save a few bob.

I also have to design a clamshell for it as well.