chiltonstar

I've split the pair twice with my 180 Mak - not easy though. A neighbour has an annoying tree which gets in the way, but I have found a spot in a field with a low southern horizon which is ok. There are not many evenings though when Antares is in the right place, there's no low cloud, and the seeing is excellent or better!

Chris

13 minutes ago, Macavity said:

I did wonder too... (what it eats)! But the above sounds plausible...
Random "dust" (from cleaning even!) is cited in the following:
http://www.truetex.com/lens_fungus.htm

Intrigue by the idea that "UV light" might kill it... Thinking of crazy
ideas like giving lenses a quick burst of "black light" every so often?
Maybe a (lower powered) UV Diode stuck inside the lens caps... 😛

Might be the ozone generated by the uv of course? I UV irradiated my lens after assembly with a mercury vapour lamp I have. 

Chris

1 hour ago, Ags said:

What does this fungus eat?

In older lenses, it used to be the Canada Balsam which cemented the components together. In an air-spaced achromat, I suspect it is the organic residues (bloom) which gradually form on any glass surface (pollen, tars and compounds from plants etc). My 102mm f13 had this problem a year or so ago. I dismantled the doublet, cleaned it with solvent and then a lens cleaning compound and reassembled the crown and flint components with new spacers which bizarrely improved the resolution cpd with when it was new (thinner spacers I think).

To avoid the problem with my 180 Mak, I store it outside in a sealed B&Q storage box with three or four silica gel sachets.

Chris

With the 180 Mak, a 7mm EP is giving x385 - I wonder if this is probably near the limit for the scope (50x per inch of aperture), so the scope optics may predominate over EP optics?

Mine certainly starts to run out of steam over x350, although this is sometimes helpful for doubles.

Chris

I use a 9x50 RACI with an RDF mounted on it, ie find the area with the RDF and then use the slomo to center the target with the RACI.

To avoid the problem of the two eyepieces being too close together, I have my 127 Mak mounted in rings so that the scope EP can be rotated to the right and the RACI EP to the left slightly.

Chris

4 hours ago, F15Rules said:

Lovely setup, Chris!

I owned an F13 Vixen 102mm a few years ago - it was called a "Pulsar". It was actually the only Vixen scope I ever owned that under performed..I actually got the lens tested by Es Reid, who suggested that the outer 10% was the problem (he said it was operating at 1/4 wave at best). On Es' recommendation, I made a mask down to 90mm and it transformed the performance and turned it into an F14.7 90mm. It was always a beautiful scope to look at, and the guy who bought it from me knew about the lens' limitations but was more interested in it as a "statement piece" for his London flat!

Vixen also made an F15 102mm frac, called the Saturn - not many of them about, but apparently totally amazing on double stars, with very little CA.. I once came close to buying one from a guy in Northumberland for £500 complete with a Vixen original full height pier and GP mount - now THAT was a gorgeous looking scope!!

Dave

Interesting! I bought mine from Vixen just as an achro doublet, and made the cell and tube assembly. The lens was pretty good, but eventually fungus invaded the edge of the lens and one of the Al tabs moved so last year I disassembled it, cleaned up the surfaces and re-assembled it. I experimented a bit with the spacers and found that a slightly thicker spacer worked a lot better than the original, and I've since had some very impressive views of 1 arcsec doubles with it, as well as Saturn and Jupiter. I have heard that sometimes the pair of lenses are not properly lined up and positioned in the cell - maybe just a rumour.

Chris

It appears on the web in several places with that name. Obviously one of the OP's favourites!

Is is a superb double star though - even my grab 'n go 127 Mak shows it in its glory with a little diamond pinpoint secondary; my 180 Mak shows more of the associated stars/companions (see other posts on this site for details, eg by John).

Chris

This is my garden - seems accurate'ish.

Chris

Quite a challenge this one and one for larger scopes! Fairly easy to locate near the North America Nebula, and perfectly positioned at the moment well above the horizon.

The separation is given as about 1 arcsec and the magnitudes 3.9 and 6.8, which I reckoned should be do-able with a 180 Mak.

First try, Tuesday with good seeing (4/5), nearby Delta Cyg was easily split and showing the secondary as a diamond pinprick, while Tau Cyg showed no sign of a secondary. The next evening (Wed), I got the faintest hint of something in about the right place, and third try (last night seeing 4.5/5) there it was in moments of good seeing at x270 and x450. Clearly separated from the primary, but messed up a bit by the diffraction pattern causing to hop in and out of view, as the secondary lies close to the first diff ring. I can't sketch very well, but the Aberrator simulation below is a fairly accurate eyepiece view at x450.

A good one to try if you are bored with looking for some detail on Mars!

Chris

1 minute ago, Red Dwarfer said:

An underrated little scope - I seen the Cassini division in my ED80 last night with a 4.8 Nagler ?

Indeed yes, mine will show the division all the way round when Saturn is high enough and appropriately tipped. They are lovely scopes for the size and weight! I use a 3.7mm orion EP for planets.

Chris

Horses and courses, I find. I love the clear views from a frac of planets, doubles etc, but as stated above, they cost a lot more per inch than a Mak and the convenience of a short tube, 180mm Mak is something a frac could not deliver. Fracs are better though when the seeing is poor as the more visible diffraction pattern from the Mak can end up as a bit of a visible jumble, for example around double stars - an issue with any scope with a significant central obstruction.

The resolution of my 127 Mak (it's actually 119 mm clear aperture) is visibly better than the resolution of my 102 mm long tube frac, but in terms of brightness on a DSO like M1, they are about the same because of the obstruction and more optical surfaces of the Mak.

Nowadays, I get the best of both worlds - I put both my 180 Mak and my little ED80 on a SkyTee2.

Chris

Chris

Welcome - don't worry about your English as it's a lot better than my Italian, and I worked there for 8 years!

Chris

I also missed this thread........

Home made OTA using a 102mm f13 Vixen achromat, circa 1980 vintage, on a Vixen mount. Still gives stunning views after 30 years use, and will be out & about for Mars in July!

Chris

I use a SkyTee2 with my 102mm f13 scope. It supports it well, but an issue is that you need to buy long cables for the alt and az axes - this is not a problem with my maks as they are short tube.

Chris

Very surprising, and excellent! I'll also have a try with my ASI224 on some brighter DSOs.

Chris

Well done John! A nice report and a nice night - I gave up here after trying for an hour or so; the Flame Nebula was only just visible, and the HH not at all. It is a target surprisingly dependent on transparency, it seems.

Chris

4 hours ago, alanjgreen said:

 

Manufacturers like to quote the "aperture rule" which says the maximum magnification for your scope if x50 per inch (25mm) of aperture - this is never achievable (nor desirable) in real life.

HTH,

Alan

I am not sure I would completely agree with this statement - look at some of the refractor posts where 50x per inch is easily achievable, and very desirable for certain planetary targets!

Chris

With a 180 Mak, up to x250 for Saturn, Uranus and Neptune, x200 about optimum for Jupiter, and up to x540 for doubles (above x400 mainly empty magnification, but it does allow the disk diameter and separation to be measured).

Chris

4 hours ago, Stu said:

Could give it a try at silly power with the Tak I guess Chris. Should try with the C925 too, it's one I've never split. It will probably end up as another Zeta Herc i.e. One I've never split!

Thanks for the post, must get out there again soon.

Should be easy with the C9.25 if properly collimated,  say at 300 times mag. 

Chris

It would be interesting to see how small a scope can split Lambda Cygni at the moment: mags are 4.73 and 6.26. sep is 0.9 arcsec, PA 359 degrees. Quite a fast mover - 390 year orbit.

With my 180 Mak it is a beautiful pair with the secondary as a very bright pinpoint alongside the primary (a very close double itself), both a blueish white colour.

My 127 Mak (true aperture 119mm) splits it on a good night, but with some difficulty and certainly not as cleanly as the 180 Mak.

Anyone split it with smaller refractors??

Chris

These little scopes deliver a lot for the price - mine has always amazed me in terms of high power views, and even of faint fuzzies! "They" say that five inches is a good aperture for much of the time in the UK because of atmospheric conditions, and I've certainly always found that. 

It will be interesting to see how you get on with the mount and scope with time - vibration may perhaps be an issue?

Chris

I have a copy of a classic Messier objects book (Mallas and Kremer), which gives an idea of what you can see deep sky with a small refractor (100mm achro in the case of the authors, your 120 ED should go considerably lower) and Sue French gives another view in her excellent book. But, as indicated above, you need a dark site and an excellent evening!

Chris

In CDSA, Talitha is shown as a triple, with a pair separated by 0.7 arcsec, and the primary 2.4 arcsec away. I see the close pair as just resolved when the seeing is excellent +. Where did your separation figure come from Nick?

Chris

5 hours ago, billyharris72 said:

A bit of Googling on this suggests bins from about 20 x 80 should do the trick. Seem to remember doing it in my Heritage 130P with a 25mm e.p. (which would be x26) though much easier around x40. As others have said it's not the distance (which is pretty wide) but the relative faintness of te companion that can make Polaris a bit tricky.

Billy.

...although some of these may have confused the nearby star SAO 305 with Polaris's partner - it's only 1/2 degree or so from Polaris. I have even seen the same thing on this forum...

Chris

6 hours ago, jetstream said:

Boy the moon is bright... it looks very clear but there must be ice crystals up there or something because I can hardly make out any stars. I'm playing with the 200mm dob and found Polaris to look at and found that I can split it down to 30x with the 25mm TV plossl. Just for a point of reference, what is the lowest mag that anyone has split this star?

It's quite a wide double (18 arcsec) so using the normal rule, any magnification above x10 or so would theoretically be sufficient, but obviously the real issue here is the faintness of the secondary. For me, if I can't see it because of the conditions, then the magnification I'm using is probably irrelevant?? Certainly at x60 with my 180 Mak (the lowest practical mag for me with this scope), it's easily visible under good conditions.

Chris