spacing info req 0.6 reducer

[pubquiz]

Hi All

I posted recently asking about suitability of using a 0.6 reducer with a 66mm scope....to cut a long story short I decided to get one and try it with my Megrez 72.

I bought one (the Altair 0.6 reducer flattener) and it arrived yesterday ...however there are no instructions or diagrams whatsover included (not good) and I am wondering about the back focus spacing.

After some searching online it seems the measurement is 55mm.....however I cant find a diagram of this exact reducer anywhere showing where to measure the distance from.

I emailed the shop and they kindly replied saying they 'thought' it was from the lens of the reducer itself  but not sure.

Usually there is a point on the reducer like a certain shoulder to measure the distance to your camera sensor from.

Does anyone have this reducer and know where to measure from? ...or a link to a diagram?

 

Thanks in advance

 

Tom

 

[LightBucket]

First of all is it a reducer and flattener all in one..

If so then it will probably consist of two sets of lens element, one is the redusing part and the other the flattener, the measurement should be taken from the centre of the two lens elements, after the reducer and before the flattener....but that position should be advertised by the supplier..

Bit if it is just a reducer, then take the measurement from the back surface of the glass.. HTH

[pubquiz]

Thanks for the quick reply LightBucket

Yes it is a reducer flattener

I agree it should be advertised by the manufacturer...there should at least be a diagram supplied with it but it comes with absolutely no literature....which is a disappointment....come on Altair Astro include some instructions!

Would be much easier if they could just say where to take a measuremnet from on the outside of the reducer,instead it looks like I will have to carefully measure the distance to each lens from each end without scratching them ...then work out what the gap between them is then mark a point on the outside corresponding to the middle of this gap to measure from!

Thanks for the info again LightBucket re the 2 lenses.

 

Tom

 

[astrosathya]

I am quite certain that Telescope Svice germany sell the same piece (it looks like the Orion USA flattener for short refractor?) under the name Long Perng 0.6x reducer flattener and its advertised BF distance is 55mm, but AFAIK, for any reducer/flattener/combo of both etc., the BF is calculated from the base of the T-Thread on the camera end of the item as it would be practically impossible to calculate the midpoint between the reducer element and flattening elements. For a DSLR by Canon, the 55 mm is easily achieved by using a simple Canon T-Ring attached to the DSLR body because the flange to sensor is 45mm and a standard t-ring is about 10mm ish.

I hope this helps because thats exactly what I use.

[pubquiz]

Hi Sathya

Thanks very much for the reply...Yes I joined an Altair Astro facebook forum today to pose the question direct to them

...I have asked 2 questions via their online form over a matter of 3 weeks and never got a reply.

Got a reply from them on the forum today saying it is 55mm but still not where to measure it from!...they say there is no diagram as they dont have access to the design!...seems a bit ridiculous as its marketed under their name.

I think you are probably right re the base of the T thread...would be nice though if suppliers could give the information about their own products!

Thanks Again

 

Tom