Focal reducer on newtonian

[Kaptain Klevtsov]

It DEFFO doesn't work with a DSLR Ant, serious coma on the bits that aren't vignetted, and half the frame is missing. You need a 2" FR for a DSLR, and even then you get distortion from a Frac. at the edge. 2" stuff doesn't work with FRs on Newts unless you "customise" them, then you can only use the centre 6mm dia. spot really.

Kaptain Klevtsov

[ribuck]

I want a reducer so that i can get a wider field of view for my MX916 CCD.

[FLO]

I want a reducer so that i can get a wider field of view for my MX916 CCD.

Perhaps the best solution is the one you have already bought - let us know how you get on

[Kaptain Klevtsov]

The only one thats worth a punt is the 1.25" screw on one available from all the usual suspects. The camera nosepiece might be too long to acheive focus anyway, but you can shorten that with a hacksaw.

The reducer goes on the camera nosepiece (try without a filter first as it will give you a better chance of getting focus) then the camera goes into the focuser. You will more than likely have to reverse the 1.25" tube on the adapter to get enough in travel, but thats easy enough. If you fit the camera then tighten the screw (which might need shortening), then fit the adapter to the 'scope, you might get somewhere.

This works for webcam sized chip cameras, so it might work with yours. Best plan is have a go.

Kaptain Klevtsov

[ribuck]

Well i have the ccd and the reducer so now i'm just waiting for the skies to clear to try and see what i get. I will post images with and without the reducer as a comparison.

Rich.

[Kaptain Klevtsov]

Good stuff Rich. As an additional request, could you take note of any difference in required exposure time if its noticeable. The good bit about FRs is that they make imaging faster.

Kaptain Klevtsov

[ribuck]

I'll do a series of exposure lengths, such as 15, 30, 60, 90 secs and we can compare to see if the focal reducers catch more data at the shorter exposure lengths.

So in theory, we should see a difference in the images. I.e. the 15 secs image with the focal reducer should capture more detail.

[ribuck]

Sod's law the weather is getting worse......it's been sunny all day whilst i've been at work then come 4pm the dark black rain clouds rolled in. Been like that all week and i bet it rains at the weekend too just to stop my little experiment.

[ribuck]

Sorry guys still no break in the weather, and apparently it's going to be bad for the next week. I'll give a progress update once the weather breaks.

[Andrew INT]

I know that this is a REALLY old thread (have the skies been bad for ten years now?)

I was looking to buy a cheap 0.5x reducer. Not really for imaging with my 8" newt and ASI 290mm camera, but to use the Polar align tool on SharpCap. Using my 102mm, F4.9 refractor it should give a FOV a bit greater than 1 degree which is the software requirement.

Has anyone tried this? 

[astrorg]

3 pages and no end testingpost? What a pity!

[Jonathan_Shields]

I am going to try this out for EAA soon ie when the clouds b*gger off.  I have a 6 inch goto dob, an ASI 585 and a cheap StellaLyra 1.25 inch reducer. I am a rank beginner but Ill give it a crack as i am after a bigger FOV. Tiago Ferreira in his Dobsonian Power Youtube channel uses a 2 inch reducer with the ASI 294 but does get some vignetting. For EAA thats less of an issue than full blown astrophotography for some I guess.

[PeterC65]

I tried using the StellaLyra x0.6 reducer with my Explorer 150PDS and Uranus-C camera and couldn't achieve focus. I needed quite a lot more in focus.

 

[Jonathan_Shields]

My scope is Flextube so i can shrink the tube if needed. I have to do that by a couple of cm to get focus with the 585 anyway. Its quite handy as otherwise I'd have to move the primary up.

[Jonathan_Shields]

I tried this out with a 1.25 inch reducer on my 6 inch dob. The field of view was a lot wider but the vignetting was shocking and not usable even for EAA. I am talking a very pronounced whitened circle. 

Maybe if everything was 2 inch including the focuser (which i dont think is possible on the Heritage 150) it would work better.

[ONIKKINEN]

On 19/03/2023 at 09:55, Jonathan_Shields said:

I tried this out with a 1.25 inch reducer on my 6 inch dob. The field of view was a lot wider but the vignetting was shocking and not usable even for EAA. I am talking a very pronounced whitened circle. 

Maybe if everything was 2 inch including the focuser (which i dont think is possible on the Heritage 150) it would work better.

The secondary mirror also greatly limits the available fully illuminated circle so a bigger focuser would not help you all the way here. Newts primarily intended for visual use already have an undersized secondary that will vignette at 1x with a decent sized sensor. Coma increases a lot with a reducer too so not really all that great an option.

If you really want to have a reducer for a newt the best option available is probably either the ASA 0.73x corrector or the Starizona Apex 0.75x one. Both are expensive and require a 2 inch focuser so also a dead end without modifications.

[Jonathan_Shields]

5 hours ago, ONIKKINEN said:

The secondary mirror also greatly limits the available fully illuminated circle so a bigger focuser would not help you all the way here. Newts primarily intended for visual use already have an undersized secondary that will vignette at 1x with a decent sized sensor. Coma increases a lot with a reducer too so not really all that great an option.

If you really want to have a reducer for a newt the best option available is probably either the ASA 0.73x corrector or the Starizona Apex 0.75x one. Both are expensive and require a 2 inch focuser so also a dead end without modifications.

Interesting it makes sense. I use the 6 inch for EAA and without a reducer it works fine it would just be good to have the extra light gathering and bigger field. It was an experiment really it was just a cheap £30 reducer. I have seen the Starizona Nexus on the Dobsonian Power channel used successfully but yeah its too pricey for me.