TMB 5mm Clone not as clear as i hoped...

[magic77]

Tried new eyepieces Tonight...TMB 5mm Clone and an 18mm BST Explorer..Explorer was crystal clear on Stars, Moon, Jupiter and M42..But the TMB never seemed to focus as well...Is this normal?..It also seemed to be affected by the cold alot more than the BST...The 10mm standard eyepiece seemed to focus better!...Will try on Saturn in Morning weather permitting.

[moocher]

5mm is pushing it a bit unless the seeing is really good. I've got a 7mm TMB and it only gets used on those odd ocassions when conditions allow. When I can its a stunning eyepiece. HTH

Alan

[John]

The seeing has been very poor of late - I've needed to use lower powers than usual on Jupiter and even then the images have not been that good.

Give the eyepiece a chance under good conditions and it will probably perform very well. As Alan says, 240x is a bit much all too often in the UK.

[spaceboy]

I went for a TMB clone 5 & 4mm EP because they are superb for the money. Given the choice I would have rather had a Televue Nagler but as Alan & John say it is only rare occasions you get to effectively use what is a high power EP. I was able to use both my 5 & 4mm a couple of Wednesdays ago when seeing was at it's best and the TBM's really come in to their own so much so that on planets and bright objects you may need a neutral or polarizing filter just to take a little glare off as WFOV EP's can suffer a little ghosting but other than that both the EP's came to focus so well I asked the question do I need the 3.2mm ?? Again as it is only rare that we get such good seeing I got my self a quality Barlow in stead.

I think once you have good skies above you, you will be impressed with both the TMB & your scope but don't expect to have a 5mm of any brand or cost in the focuser all that often. You need a high power EP for those nights of good seeing to really get the most from your scope so don't think it's money down the drain but you really could do with the 7-9mm as this would see more practical use under our skies.

Just to give you an idea of the difference between the magnifications in your scope will give you a better idea why the 10 & 18mm could come to focus. The 5mm at x120 more magnification than the 10mm was too much for the nights seeing but a 7mm at x171 may on this occasion worked better for you. If you have a barlow lens then an option could have been to x2 the 18mm to 9mm for x133 magnification.

5mm = x240

10mm = x120

18mm = x67

7mm = x171

Hope this helps.

SPACEBOY

[magic77]

All your replies have helped thank you....I was up looking at Saturn this morning and it was the same as last night...18mm and 10mm focused nicely...But the 5mm always seemed to be "out of focus" as it were(hazy)..But now you have answered my question it has become clear to me!!...Thanks and Merry Christmas to you all...

[russ]

You could always add a second TMB, like the 8mm version. Would give 150x, which is a more usable magnification most nights.

[magic77]

Yes i could add a 8mm TMB..But i have just had a new Telescope this month, and 2 eyepieces..You can only hide so many Bank Statements and new Pieces of kit before you get a telling off from your other half!!......If i were to get an 8mm Eyepiece would you recommend the TMB or the BST Explorer..Last night when i tried the TMB and Explorer for the first time(it was -4)..The TMB seemed to mist up alot more than the Explorer.....

[russ]

I didn't find there was much in it really between the two, the TMB was perhaps a smidge sharper. I had some slightly annoying reflections in my 8mm BST which the 12mm and 18mm models didn't have. So i bought the 8mm TMB to replace it. Reflections aside, they were equally sharp across the field of view. I sent the 8mm BST back as i suspected it was lemon.

[spaceboy]

You will notice some EP's will mist up more so than others. This is normal. You have to think of all the different elements that come in to play. Lens size, how many lenses and in how many groups. Build and materials used, where the ep's have been kept prior to observing etc, etc ,etc. They do make dew bands for ep's but I intend to keep hand warmers in my ep case. A cold ep and a warm eyeball your always going to get misting. Have patience you will get in to a routine to what works best for you Coming from a tracking EQ mount to a manual dob is my biggest qualm, but again it is some thing I would get used to.

Have a Merry Christmas all!!

SPACEBOY

[nightfisher]

I just got my TMB 8mm, looks superb, cant wait to try it out

[Ags]

I have a 9mm and 6mm TMB clone, and I love them.

[magic77]

Managed to Have some good views of Saturn on Christmas day(was up at 5.00am for some reason, couldnt sleep!)..Even though viewing conditions were not perfect i could definately see the potential of my 5mm TMB...Cant wait for a real clear night/morning...Happy New Year to All...

[spaceboy]

Hi Magic

Have you had another chance to give the TBM a go ?? I have forgotten what stars look like myself the clouds seem to love hanging out over my way. The season will be over before it's begun for me.

Happy New year,

SPACEBOY

[Telescope40]

Hi. I recently tried a 8 mm BST against the TMB. TMB won out, for what its worth. Thx John

[jasonp]

I too bought a 5mm TMB and was bitterly dissapointed. Now I realise that it is pushing it for max magnification for seeing conditions. I will most probably get a 7mm Next.

[spaceboy]

On paper a 200p should push 400x magnification but in reality the best you ever get in most telescopes is 200x due to seeing conditions. On those rare occasions the atmosphere is settled and the transparency is good a 200p will perform superbly up to 350x. It's on these nights when you wish you had a 3.2mm, 4mm or 5mm to drop in the focuser. My reason for buying a TMB EP was not just that they have a good 58' FOV with bright sharp images to the edge and more than enough eye relief for a short focal length it was because most importantly they gave me all this for only £38 to my door. On those rare nights of seeing I know I have a good performing eye piece that will extract the very best views from my telescope. On those usual nights of frustration when the sky is crystal clear but the turbulence 2 miles up is turning my view in to a puddle I know I have only £38 sat in my case wasting space and not a £200 Nagler. On most nights I can just about get an acceptable image out my scope with my 6mm Radian 167x and although you may get the occasional glance of calm air I wouldn't be immediately reaching for my 4 or 5mm. You will know when you have that good night as when you do you will find 3-5mm's will be the only EP you will want to use.

Another alternative is to buy a 10mm EP and 2x Barlow that will give you 5mm when you need it but putting more glass in to the mix has it's own debates and Barlow's aren't with out there own down falls. As I have always said... what works for one may not work for another but I am taken back by how good TBM clones are for the money and if it wasn't for the fact the wide FOV of a nagler makes using a dobsonian so much easier I would have the full set of TBM's.

[nightfisher]

well said spaceboy, the very same reason i got my 8mm tmb, for the rare occasion when i can go down below a 15mm ep without having a lot of money sat idle