Testing Flattener Reducer - Daytime ?

[Eddie Jones]

Hi All,

I bought a  "Planostar 0.8x v2" flattener / reducer secondhand, it came with no instructions (and I cant find anything definitive online)

I will need to work out the correct distance required to my Canon DSLR sensor.

I've found what appears to be almost identical item - so will try these settings first:-
https://www.teleskop-express.de/shop/product_info.php/info/p5965_TS-Optics-REFRACTOR-0-79x-2--ED-Reducer-Corrector-fuer-APO-und-ED.html

Is there a method for checking correct distancing in daylight ,  or have I go to wait for the next cloud free night ?

[MarkAR]

Have you checked on Altair Astro's website.

https://www.altairastro.com

[Eddie Jones]

11 minutes ago, MarkAR said:

Have you checked on Altair Astro's website.

https://www.altairastro.com

Hi Markar,

Yes, been over there site quite a few times.  

I did email Altair with a picture, they  helpfully told me it would fit my scope (Starwave 110ed) - to be fair - that was the question I asked!

I'm sure I can get this sorted out, just keen to get on with this, as I've also finally got a guide camera to get working as well !

Wondering if I can paint a grid of dots on the garden fence to test or something ?

[alacant]

23 hours ago, Eddie Jones said:

Is there a method for checking correct distancing in daylight

Hi

Set the distance using T2 threded spacers according to the focal length of your telescope. I'd be surprised if you needed much more than just a T2 adaptor, giving you the popular 55mm spacing. Screw the FF directly to it.

Point at Cygnus and see what the stars are like around the edges. If there are issues, post the frame here.

Cheers and HTH.

 

Copied from your link:

Back Focus - distances from the T2-thread to the camera sensor

depends on the focal length of the telescope:

♦ Focal Length to 350 mm .... 70 mm
♦ Focal Length to 420 mm .... 65 mm
♦ Focal Length 450-500 mm ... 61 mm
♦ Focal Length 510-600 mm ... 58 mm
♦ Focal Length 610-700 mm ... 57 mm
♦ Focal Length 710-790 mm ... 56 mm
♦ Focal Length from 800 mm .. 55 mm

Edited July 8, 2020 by alacant

[MarkAR]

Looks like you need a total of 56mm, you might just need to add a 1mm shim. DSLR + adapter is usually 55mm.

[michael8554]

During the day use the sun reflecting off a ball bearing as an artificial star.

Focus mid frame, then take shots with the "star" in each corner.

Analyse, adjust, repeat.

Michael

[Eddie Jones]

On 08/07/2020 at 00:58, michael8554 said:

During the day use the sun reflecting off a ball bearing as an artificial star.

Focus mid frame, then take shots with the "star" in each corner.

Analyse, adjust, repeat.

Michael

Sounds perfect - Will start at 55mm as suggested by alacant & MarkAR and work up from there. Much prefer setting things up slowly and carefully in daylight (also easier to find a dropped black M48 ring in the grass) Now I'm waiting for a clear day as well as clear night.  

Edited July 9, 2020 by Eddie Jones

[GalaxyGael]

Reviving this old thread as I dealt with a similar issue. Maybe outdated, but might be useful for someone else searching.

This type of reducer came in two flavours - a 4 element and a three element. The latter is more common now as the 0.79x reducer. And it works with the focal length spacings outlined above.

However, if it is the 4 element one, the spacings are different (larger). That reducer usually came with a T2 spacer already screwed on, that allowed 55 mm spacing from there, i.e. the reducer + ~8.5 mm spacer that was 63.5 mm or thereabouts, much larger than the 58 mm that the three-element 0.79x reducer requires for 510-600 mm scopes (to use one example).

Here is the 4 element one, with the (for 80ED) spacer attached. It specified 55 mm, when the spacer is used. Otherwise, 63.5 from the end shown in your picture. It works great with my 600 mm f/6.7 scope, but the 3 element one at the same spacing gave cross (astigmatic) stars and I had to reduce it to to ~58 mm in the 3 element 0.79x case.

https://www.astroshop.eu/flatteners-correctors-reducers/tecnosky-0-8x-four-elements-flattner-reducer/p,58722

[alacant]

On 29/08/2022 at 10:25, GalaxyGael said:

the 4 element one

Hi

Long shot, I know after so long... Does anyone have the spacings for the 4 element version?

Apologies in advance for the noise; duplicates this:

 

Edited June 22, 2023 by alacant