Using a Barlow with Finder/Guider???

[Pomerol]

I currently use a 9x50 Skywatcher "finderscope" to guide my Mak-Newtonian 190mm FL 1000mm and have very satisfactory results. I am at the early stage of investigating buying a 250mm R-C which has a FL of 2000mm.

Guiding the R-C with the 9x50 would be from the little I have read on this subject very challenging.

I would prefer not to go down the OAG route at this stage  so am looking for information on whether it is possible to fit a Barlow between the QHY5 camera and the 9x50?

My searches have so far  come up with nothing so any information/experiences would be most welcome.

Ian S.

[lensman57]

You are buying a specialised  scope for £2000.00 + and you are trying to save £60.00~£70.00 on the price of an 80 mm F5 scope for guiding. I believe there are some being sold on the eBay for about £45.00 now. I would also seriously think about replacing the QHY5, a few years ago it was an economical option  and I am sure that the Cmos sensor has well past its sell by date now.

A.G

[Pomerol]

I had an F5 70mm refractor as a guide scope which  I sold a year ago when I found the 9x50 gave me better results and being much lighter gave  no "differencial flex".

[lensman57]

I had an F5 70mm refractor as a guide scope which  I sold a year ago when I found the 9x50 gave me better results and being much lighter gave  no "differencial flex".

I agree 100% but the 50~60 mm guide scopes are effective up to about 1000mm of FL, by far and large the best guiding solution for  your proposed scope is to use an OAG with a LodeStar as you can not afford guiding errors at 2000mm of FL. I think that anything around 500mm of FL will do for guiding if the fixings are rigid.

Regards,

A.G