KEJ

12 hours ago, Louis D said:

Well, the galaxy looks quite nice indeed.

Too bad about the stars.  It looks like the various color layers need shifted radially.  The shift grows with increasing distance from the center.  I recall Helmut Dersch had a feature in his Panorama Tools to do just that.

Thanks and I have never heard of that/him before.

This was more of a test last night, but with the 6.3 Reducer at 105mm or 107mm to the join, I had a FL of 1304mm when it plate solved(info in App and FITs header file), which I believe equates to the Reducer working at 6.4 which is possibly the best I'm going to get.

Meade 2034mm FL 1304/2034 = 0.641

Sunflower Galaxy M63 Approx 27 million LY away and 100,000 LY wide.

Not the best image as I only managed about 50mins of data last night and a fair amount of fringing on the stars(just can't get the staff).

Captured using Meade 8" SCT with a 6.3 Reducer with a FL of 1304mm. ASI533 MC Pro, guided with the help of the ASIAIR.

Bortle 6.

Managed to get a small break in the cloud. 

Steel ruler, 6.3 Reducer and A4 paper in hand, I took an approx measurement of 220mm FL, which I think equates to mine having or requiring a BF of 105mm or 107mm approx to the join between the Reducer and T-Adapter.

Optical train should now be set and hopefully clear skies tonight.

Thanks again for everyones comments and advice.

3 hours ago, Stuart1971 said:

Yes, try and work out where the actual shoulder of the reducer is and yes it will be a couple of MM inside the T adapter….👍🏻

Brilliant and thanks once again.

I will bring everything down and alter once again.......

Job completed and now the wait for the weather......

1 hour ago, michael8554 said:

Rule-of-thumb is to focus the sun on a flat surface with just the FR, to roughly measure the focal length of the Reducer.

Some figures that most seem to agree on :

210mm FL,  Back Focus is about 105mm.

105mm FL, Back Focus is about 85mm.

Adjust for best corner star shapes.

I posted the spec sheet for the f/3.3 on April 3rd.

Michael

 

 

Thank you also for the prompt reply and info.

I have never tried the Sun trick and whilst the 105mm figure is mentioned, I was exactly unsure up to exactly where as previoulsy I had always measured to B from the camera sensor.  

So I guess all my various tests were pretty much 10-12mm out all the time.

Thanks 

3 hours ago, Stuart1971 said:

Ok, so with the 6.3 reducer, the back focus should be approx 107mm and the measurement should be taken from the base of the rear threads on the back of the reducer, as for the 3.3 the measurement should be taken from the same place, but the back focus distance is much shorter, there is a spacer set than comes with this reducer, which gives the exact correct back focus…

position A in your drawing is correct to measure to 👍🏻

 

 

Stuart hi

Thanks for the prompt reply and info.

6.3 Reducer

Is it safe to say the join, where the T-Adapter meets the Reducer or just step back into the T-Adapter collar a few mm ?

I will have to take it apart to check.

3.3 Reducer

I had a 15mm and 30mm tube/spacer that came with the adapter. I still assumed I would have to make allowances for the camera as I again assumed the older camera sensors could have been closer etc - fair point.

Thank you

Not sure if anyone out there can give me a definitive answer on three hopefully simple questions.

Background

I have a Meade 8” SCT F10, ASI533 MC Pro camera and Hirsch 6.3 Reducer – see the attached.

Q1)  Back Focus Distance

Does anyone know the correct back focus(BF) for this setup as I have heard values from mentioned from 85mm, 88mm, 105mm and 115mm, when measuring from the camera sensor to the Reducer?
 

Q2) Measure to Where

When measuring, the camera end is simple as I know from the sensor “C” to the top of the camera spacer “D” is 17.5mm.
Should the measurement at the Reducer end be to point “A” or “B” on the T-Adapter ?

Example

Take the 105mm or 115mm BF figure I have used, now depending how you measure, to point “A” or “B” then that could be the approx. correct distance.

Q3) Meade 3.3 Reducer

In addition, I have a Meade 3.3 Reducer and once I know the correct point to take the measurement at the T-Adapter end is, does anyone know the BF distance for that potential setup as well ?

(With the 3.3 Reducer I could also possibly try it with one of my planetary cameras which have smaller sensors & more out of interest).

Hopefully thanks

On 06/04/2023 at 08:02, ollypenrice said:

I gave one away. If getting a large telescope with an F ratio of 3.3 were as simple as screwing one of these reducers onto an SCT, it is highly unlikely that anybody, anywhere, would use anything else! 

lly

You could be right........Its just that I have one and I was determined to try and get it to work. Parked up for the moment......

5 hours ago, Louis D said:

Kind of cool looking in a hyperspace jump or blackhole suction sort of way, though. 😁

Mine will be going down a black hole if I can't sort it out.

I'm parking the 3.3 issue for the moment, so back on the WO Z61 and maybe a crack at Venus/Moon with the Meade over the next few nights if its clear.

Thank you, yes I agree on that.

I have been using picture as well previously.

So from last night a poor image

7 minutes ago, Stuart1971 said:

yes, if that  screws directly onto the reducer then from the corner edge of the reducer, as every mm will make a difference….

Thank you........

6 minutes ago, Stuart1971 said:

Yes, the glass does stick out a bit more, but the shoulder at the base of the threads  is at the back of the first lens, which is where the measurement should be taken from, as this is a reducer and a flattener in one, with two sets of lenses, so the measurements is taken after the reducing lens but before the flattening lens…HTH

the red line is where you should measure from

 

Blimey, thats interesting and I would have never in a month of Sundays figured that out. - thank you.

So looking from above at the optical train, where the crack/join/seam is between the T-Adapter and Reducer?

Your red line on the right hand side is say on the threads of the Reducer?

3 hours ago, michael8554 said:

Hi KEJ

The Meade f/3.3 Reducer was designed for the tiny sensors of the 1990's.

So I'm not sure what the stars in your 1" Square camera are going to look like !

Michael

Thank you......I did read that previously. But I'm still trying with the 533 and that was going to be a try fallback with my planetary camera.

2 hours ago, Stuart1971 said:

First of all do you have the correct spacing or is it more than you think as these reducers in the f6.3 version have a 107mm backspace, secondly your red line is correct, it should be measured from the shoulder of the reducer assembly, as the bottom of the rear threads… 

you should be including any space in the backspacing measurement, that is from the sensor to the shoulder of the reducer, any space in between….

Once I know where to measure from, which I do now........I can at least concentrate on the getting the spacing correct.

1 hour ago, Stuart1971 said:

First of all do you have the correct spacing or is it more than you think as these reducers in the f6.3 version have a 107mm backspace, secondly your red line is correct, it should be measured from the shoulder of the reducer assembly, as the bottom of the rear threads… 

you should be including any space in the backspacing measurement, that is from the sensor to the shoulder of the reducer, any space in between….

Thanks for the prompt reply.

I have a 6.3 reducer and I find 105mm BF is perfect(well with my dodgy eyes).

However, with the 3.3 Reducer I hear or read so many conflicting comments, so I have with the bad weather been trying to grab the odd picture and relying on the star patterns until I get a definitive answer. Currently the outer stars are all slightly radiating outward, which I believe suggests the gap was too small.

Hence why, I was just going to try 58mm approach later.

Question

Whilst you have answered my question(thank you) the glass or last lens of the Reducer I assumed sticks out slightly more, thats why I was possibly confused, but I will take your advice.  And just to be clear, on my picture on the Reducer,  I have the raised band/collar where it has Meade printed on it, to the left is the crack/join where the reducer meets the T-Adapter, that is where I believe the tread would be if they were separated/unscrewed, if that makes sense ?

Thank you

2 hours ago, Cornelius Varley said:

Done the reformatting for you. Tip, if you are copy/pasting from another source use "paste as plain text" to remove existing text formatting.

Back now and thank you, hopefully I'll remember.

A question regarding back focus(BF) when using a 3.3 Reducer and any comments or advice would be appreciated.

So last night I was intending on trying the 58mm approach as the BF distance, unfortunately it was way too cloudy, so that test is on hold.

In the meantime and regarding measuring, if you see the attached picture of my ASI533 and the distance between 1 - 2 = 17.5mm (sensor to top camera spacer).

Questions

When measuring or calculating distance and allowing for the 17.5mm (sensor to top of the camera spacer), should I measure to the Green, Yellow or Red lines/indicators I have added?

Example

Whilst this pictures probably show one of my earlier tests,  let’s say the gap between the camera spacer and the T-Adapter was approx 10mm at thats the spacers I am using.

Therefore, camera sensor to Green line could be 17.5 + 10 = 27.5mm

To the Yellow, could be 17.5 + 10 + 10 = 37.5

To the Red, could be 17.5 + 10 + 10 + 5 = 42.5

I am always slightly unsure where I should be measuring to exactly at the T-Adapter end ?

People say to the last glass lens of the Reducer(camera end) so I tend to guess and with the 3.3 you have to be more precise.

Thanks in advance

* where the spacer is closest to the T-Adapter, there is a tiny few mm collar, should I be allowing for that as well ?

** Or

Actually, should I be measuring inside the T-Adapter to where the tread ends inside the tube?

Sorry for all the questions and any comments much appreciated, I cut and pasted, the text has gone weird .......have to pop out will try to edit later

I tried using Siril and added about 500 pics.......still haven't got it weighed off for adding FLATs mind....

I grabbed a few more images the night before last.....next I will try to incorporate them with my others 

7 hours ago, Mike Q said:

Isn't that the way it always is.  If it isn't the moon, it's the clouds.

Or your not going outside again tonight!!!!!!!

The Moon has other plans for the next week or so.....

On 06/05/2022 at 21:25, dillon80uk said:

Wow amazing pics guys 

Lets see if we can add to them tonight

On 06/05/2022 at 18:23, callisto said:

Nice 

It's great when everyone has a go at the same target

On 06/05/2022 at 18:22, Littleguy80 said:

Great image. The SN is super bright compared to the host galaxy. 

Very true.......I'm hoping to grab a few more subs tonight as well.......slight cloud here though at the minute.