Alnitak with ED80

[NGC 1502]

During a recent unexpected late night clear slot I was out with my ED80.  I’ve often found Alnitak (easternmost star in Orion’s belt) quite tough to split in my 10” Dob. The 10” is excellent quality and is kept well collimated and fully cooled before attempting anything difficult.

During that recent ED80 session I was enjoying lots. Then I thought I’d try to split Alnitak, not expecting to succeed. At 120x I thought I could detect the secondary. Going to 240x the split was confirmed, intermittently but clearly in moments of half decent seeing.

Just wondering about other visual observers experiences?

[Alan White]

That is an interesting result Ed, a no go with the 10” which I know is good quality, yet success with the ED80, which I also know to be a good one.

Was this a difference in seeing or similar?

[Geoff Barnes]

Alnitak is quite a tough challenge, mostly because of the glare from the main star (a bit like Sirius and the pup) but I do recall splitting it last year. I would probably have been using my 6.5mm Morpheus giving 275x in the 12 inch Dob, so similar to your success. I look forward to having another go in a month or so when Orion is clear of the trees.  😀

Edited November 13, 2021 by Geoff Barnes

[Mr Spock]

I suspect it's a mixture of increased brightness in the Dob and less than ideal seeing conditions creating too much glare. Try the dob again with a ND filter or sub aperture mask.

[RobertI]

I had exactly the same experience a few years ago, with my 8" SCT not being able to cleanly split it but my 4" achromat seeing a clean split. I think Alnitak is one of a few examples of doubles where the bright primary makes it very tricky.

[Alan White]

Or an example of where a refractor has an advantage

[lunator]

It is a tough split. I have managed to split it in my 8" Newt and OMC250. It usually took about x188 magnification.

I haven't tried my ST80 yet.

Cheers

Ian

[NGC 1502]

6 hours ago, Alan White said:

That is an interesting result Ed, a no go with the 10” which I know is good quality, yet success with the ED80, which I also know to be a good one.

Was this a difference in seeing or similar?

Apologies because my opening post wasn’t clear.  My 10” will spilt Alnitak but not at every attempt, needs reasonable seeing plus of course at as high an elevation as possible. For those not familiar with Alnitak there’s a faint field star much further away that could perhaps confuse observers.  Alnitak’s secondary is tight in to the primary, my double star atlas says the separation is 2.4 arcsec which is not all that close, it’s the magnitude difference that’s the problem, as previously mentioned.

The above was my first try with the ED80 and I was surprised to succeed.  Of course I’m not trying to say an ED80 will do everything as well as a 10”.  Both scopes are “better” than the other according to what’s asked of it.

Ed.

Edited November 13, 2021 by NGC 1502
Correction