Image tilt

[RolandKol]

43 minutes ago, Thalestris24 said:

Anthony - try an artificial star:

Edit: Actually, what I would do is make a small cluster so that would show up the distortion pattern better, I think.

Louise

you need quite a space for that....

I saw calcs somewhere, 130PDS+ASI1600 needed at least 20m distance... his setup will probably need more or less the same....

[ollypenrice]

1 minute ago, RolandKol said:

you need quite a space for that....

I saw calcs somewhere, 130PDS+ASI1600 needed at least 20m distance... his setup will probably need more or less the same....

A driveway will often be long enough. If it ends in a garage you could put the ballbearing at the closed end of the garage for better contrast but I've done it outside. The first time I did this test was in a condom warehouse. Don't ask!!!

Olly

[Thalestris24]

1 minute ago, RolandKol said:

you need quite a space for that....

I saw calcs somewhere, 130PDS+ASI1600 needed at least 20m distance... his setup will probably need more or less the same....

Yeah, something like that - shouldn't be too difficult to arrange something... I wish I could but I live in a 2nd floor flat which is severely limiting on many accounts. Anthony has an ed80 + dslr, so similar, I think. I reckon it would make life a lot easier for anyone trying to set flattener spacing.

Louise

[Thalestris24]

1 minute ago, ollypenrice said:

A driveway will often be long enough. If it ends in a garage you could put the ballbearing at the closed end of the garage for better contrast but I've done it outside. The first time I did this test was in a condom warehouse. Don't ask!!!

Olly

? 

[ollypenrice]

29 minutes ago, Thalestris24 said:

? 

Well I had this friend, you see, called Captain Condom - at least this was his business name - and he had a long warehouse. But once when my car was stolen he loaned me his van to go to school in. This made me a superhero amongst the kids... 

Olly

[Thalestris24]

1 minute ago, ollypenrice said:

Well I had this friend, you see, called Captain Condom - at least this was his business name - and he had a long warehouse. But once when my car was stolen he loaned me his van to go to school in. This made me a superhero amongst the kids... 

Olly

Clearly, size is important

[gorann]

On 03/04/2019 at 19:51, Anthonyexmouth said:

No, I've got this one

https://www.altairastro.com/lightwave-0.8x-reducer.html

 

Just be aware that the ideal distance to the chip may vary with the focal length of your telescope, as seen on the info for this reducer from TS (which is likely to be similar to yours from Altair):

https://www.teleskop-express.de/shop/product_info.php/info/p5965_TS-Optics-PHOTOLINE-2--0-79x-Reducer-4-element-for-Astrophotography.html

[Thalestris24]

This is an interesting read (80ed + lightwave 0.8x towards the bottom) though he doesn't mention adjusting the spacing at all:
https://astro.ecuadors.net/refractor-reducers-televue-trf-2008-vs-altair-lightwave-0-8x-on-sw-evostar-80ed-equinox-80-ed/

I might be wrong, but I've always assumed spacing is 55mm unless otherwise mentioned - as with TS. But there is always the +/- (0.5 - 1mm) fiddling!

Louise

[Anthonyexmouth]

Ok, can someone with a more experienced eye comment on this please

 

[vlaiv]

Almost perfect?

I think that correction is about as good as you will get with that FF/FR. I think I still see a trace of tilt, but it's so minor that I'm not sure if it's worth pursuing.

You should stack multiple subs - any slight distortion in the corners will probably be masked by the seeing after stacking multiple subs.

[Anthonyexmouth]

Just now, vlaiv said:

Almost perfect?

I think that correction is about as good as you will get with that FF/FR. I think I still see a trace of tilt, but it's so minor that I'm not sure if it's worth pursuing.

You should stack multiple subs - any slight distortion in the corners will probably be masked by the seeing after stacking multiple subs.

thats made me happy and given me the confidence in this FF to look for a cooled camera... unfortunately for my credit card.. lol. 

still annoyed that i followed the image chart on AA website that said it was too far away. i spent money on a low profile t ring, almost bought a load of extension tubes i didnt need. i'm glad i saw the baader t ring on amazon and with their easy returns gave it a go. 

[Thalestris24]

56 minutes ago, Anthonyexmouth said:

thats made me happy and given me the confidence in this FF to look for a cooled camera... unfortunately for my credit card.. lol. 

still annoyed that i followed the image chart on AA website that said it was too far away. i spent money on a low profile t ring, almost bought a load of extension tubes i didnt need. i'm glad i saw the baader t ring on amazon and with their easy returns gave it a go. 

Measuring the distance from the sensor line to the front of your original t ring would have shown you something was amiss straightaway but - live and learn! Never assume things are what you believe them to be...

Louise

[carastro]

Really glad you have got this sorted.   Any chance of getting a refund/exchange on the wrong items.

Also out of interest, (got a bit lost on this thread), were those distance diagrams, the wrong way around for what spacing you needed?

Carole 

[Anthonyexmouth]

3 minutes ago, carastro said:

Really glad you have got this sorted.   Any chance of getting a refund/exchange on the wrong items.

Also out of interest, (got a bit lost on this thread), were those distance diagrams, the wrong way around for what spacing you needed?

Carole 

yeah completely wrong. I was too close, the baader was a little thicker and that sorted it. 

i'll keep the bits i bought. just in case. 

[carastro]

Quote

I was too close, 

So that is the same as I found.  Strange these diagrams have been published the wrong way round, and very misleading.

Carole 

[Anthonyexmouth]

4 minutes ago, carastro said:

So that is the same as I found.  Strange these diagrams have been published the wrong way round, and very misleading.

Carole 

especially as its one of the pictures on the AA web page for this flattener. misleading and very disappointing.