2in filter adapter - unable to reach focus.

[engstrom]

So after initial successful attempts imaging (finally getting my raspberry pi to behave itself) it seems a further step to improve focus and image quality is the addition of an ir/uv cut filter. I bought a 2in filter and one of these after reading comments but i find now I can’t achieve focus. I have the filter in the adapter fitted into the draw tube in the 2in collar, the focal reducer attached the adapter along with the 55mm bf extenders and then the camera. The image gets near focus but the I run out of inward travel in my evosfar ed80. 
have I basically got the purpose of this adapter wrong or am I making a mistake in my image train?

[david_taurus83]

What camera are you using and what spacers? Should it not be 55mm back from the reducer to the camera sensor? Adding a filter would theoretically push the focal point out a bit.

[engstrom]

It’s an asi585. I have 55mm between then camera and the reducer. The filter is before the reducer attached directly to the draw tube.

[michael8554]

Do you have the correct 0.85 Focal Reducer for the ED80 ?

Without the new adapter and any filters, attach the FR to the focuser threads, and add the ASI 585 and FR at 55mm.

How many millimeters of travel are left in the focuser ?

But you said:

"I have 55mm between then camera and the reducer"

Do you mean "55mm between the camera sensor and the reducer" ?

If you have 55mm to the camera, that will be 65.5mm to the sensor.

Which may explain why you can't focus ?

Michael

[engstrom]

Ah! I thought I did have the correct bf from the sensor but I’d forgotten I needed to add an adapter between the camera and the extenders. 
Now I just have to wait another three months for a decent night’s viewing.

Thanks for the impetus to take the train apart and recheck. Hopefully that might sort it.

[AstroMuni]

On 30/04/2024 at 22:20, engstrom said:

I thought I did have the correct bf from the sensor but I’d forgotten I needed to add an adapter between the camera and the extenders. 

Its indeed a tricky business to attach 2" filters to the camera. Several of them come with the ability to attach a 1.25" filter but no provision for a 2".

As you are introducing the IR cut filter after the reducer (ie filter, reducer, camera), the previous arrangement that you had for bf should still work. I opted for a filter drawer to get around this issue of achieving focus etc. The SVBONY 226 is quite inexpensive and comes with an additional drawer.

Edited May 2 by AstroMuni

[engstrom]

Ironically that’s where I started off. I ordered a 226 but the delivery date kept being pushed back until it’s now marked as unavailable via Amazon. It seemed to be out of stock everywhere unfortunately.

[AstroMuni]

6 minutes ago, engstrom said:

Ironically that’s where I started off. I ordered a 226 but the delivery date kept being pushed back until it’s now marked as unavailable via Amazon. It seemed to be out of stock everywhere unfortunately.

Amazon seem to be selling a 2 pack version though 😉 so you could try ordering directly via SVBONY site

Edited May 2 by AstroMuni

[engstrom]

At the moment I think it’ll stick with the adaptor I have and when the skies clear give it another bash and hopefully I can get focus.

I’m reluctant to bag that one on Amazon as I don’t really need a dual pack plus there’s a 1-2 month dispatch time and the one I originally ordered from the Svbony Amazon us store kept getting pushed back.

[AstroMuni]

1 hour ago, engstrom said:

I’m reluctant to bag that one on Amazon

I dont think I was clear enough in my previous post... I wasnt suggesting you buy the dual pack; 🙂 Its just odd that they dont have stock of single pack but are willing to sell dual pack !

Also the SVBONY site I was talking about is https://www.svbony.com/sv226-filter-drawer/#W9184A-F9127A