Struggling with new 6mm TMB EP

[johnkirkpatrick]

I have bought a 6mm tmb planetary and cant seem to get it to focus properly, I dont think its collimation as my other ep's (see sig) are fine and stars are pin points, I think I may have a dud??

when viewing Jupiter last night i just could not get it to focus and struggled to get any clear detail infact my 20mm meade 5000 swa was great but wanted that bit more mag as I should be able to get to x200 easily with my scope.

Any thoughts guys??

John

[Ben Ritchie]

What was the seeing like for you? 200x is often fine, but not always - there are times when my 6mm Radian is too much for my 200p.

[Merlin66]

Try it on a couple of double stars.....

[johnkirkpatrick]

seeing was quite good I also had tried the moon and i took the mag but wasnt very sharp even in the centre of the fov, also pointed at random stars and just not quite pin point.

[johnkirkpatrick]

Try it on a couple of double stars.....

I tried it on the double's in the plough and just couldnt get it sharp at all although i could clearly split them?

[WayBig]

from your kit list, its the shortest focal length eyepiece you have - could it be that the "sweet spot" of good focus is tighter than the others due to that

I have that sometimes with a 5mm eyepiece, where it seems that the slightest touch on the focuser is enough to move it from too far in to too far out.

[WayBig]

I've also exhaled on an ep's one cold night - causing condensation, then spent the next 30 mins wondering why everything was soft focus....I'll assume I'm the only one daft enough to do that though and that your problem is a real one!

[mdstuart]

I just think its the mag level and seeing. All eyepieces shorter than 9mm seem to haev this effect, I have plossl, orthos and the TMB's and its the same in all. Just occassionally in good seeing things sharpen up..

The dew issue is so true though...been there done that..

Mark

[johnkirkpatrick]

Im gona try again tonight so will post here laterone and see how it goes. hoping for some dso's tonight

[brantuk]

Hi John - to get round this sort of thing I use a hyperion 8-24mm zoom ep. I start at 24mm and gradually move down thru each stop judging the seeing and sharpness as I go. If I can reach 8mm at good contrast and sharp focus - then I'll try the 5mm Radian. Maybe you can go thru your ep's in a similar way - 20,15,10mm and then the TMB 6mm if it's still sharp

[kidlands]

I was having the same problem with my WO SPL 6mm last night too so maybe atmospheric or as waybig said condensation for both of us.

[Ogri]

I had the same problem last night, and it was really heavy dew.

Both 'scopes had to come into the house to dry out overnight.

I think I'm going to get one of those 12v hair dryers before long.

eta: luckily I had tried out my 'new to me' 38mm 2" 70 degree earlier, or it might have been panic stations. With the UHC in as well, in the 200p dob, the CA on the moon was mind bogglingly bad. Took the UHC out, and it was totally fogged up. Had a nice quick view of the Wild Duck cluster that was clear, and then things all fogged up again.

[Moonshane]

I agree with Mark. It's likely to be seeing conditions which are rubbish currently and severely restrict magnification. with both my dobs I have been struggling to get above 145x (11mm Plossl) if I want to retain any sharpness on Jupiter. the moon is really quite low at the minute too so there's the atmosphere problem with that.

I can definitely get more magnification in the spring based on my experiences earlier this year. will be interesting to see what winter brings with the sharp and clean winter air. frozen noses seems to mean better conditions.

I collimate every time I use the scope the same way so can confirm it's not that.

I'd persevere and have the 6mm in reserve for those rare nights when you can get above 200x generally. when the moon's a bit higher it will be useful then.

[ollypenrice]

You really need to try another EP of similar focal length back to back. In general net browsing, though, I've come across a good number of people saying they have returned sub standard TMB items but been happy with the replacements. As I've said before, this is no way to respect the late Thomas Back who was, by all accounts, a perfectionist.

Olly

[johninderby]

Is this one of the eBay TMB 6mm eyepieces?

Reason I ask is that they have been a number of reports of some of these eyepieces purchased on eBay not being up to the usual standard of the TMB 6mm Type II with soft views and or other defects.

Curiously enough the TMB clone eyepieces all seem to be very good with consistent quality.

John

[Ogri]

As an aside, are there any of these 12v hair dryers to avoid, or are they all pretty much of a muchness?