BST 8mm focus issue?

[robster]

Just received an 8mm BST from STL, and wonder if this is normal (I'm a newb, and this is a gift for my son BTW). This is to go on a SW 200PDS.

I wanted to check the EP, so popped it on the scope and pointed it at a tree on the horizon some 1.5 miles away - and just can't get a really crisp focus. Is this normal for daylight viewing, or should it acheive "crispness".

Many thanks

Rob

[Bart]

Should be crisp Rob.

[Stephen]

You may need to consider the collimation of the scope first, do you know if it's been done recently?

[russ.will]

And also don't forget that 1.5miles of the densest, dirtiest, unstable part of our atmosphere is in the way.

Russell

[Naemeth]

Try and focus at a nearer tree if possible, if you get the same results with all your EPs, your scope may need collimating.

[robster]

My 28mm SW EP is perfect over the same distance.

Alan at Skies The Limit is kindly sending me another EP, as he says it doesn't sound right....great service!

Thanks all

Rob

[Richardisgreat]

Just a thought make sure there are no warm currents in the scope by leaving it outside for at least 40mins to cool before useing. (sounds like making a cake ) lol clear skies

[PorkyB]

I was having trouble focusing my BST 8mm, until I realised that the problem was vibrations from my fingers on the focusing knob. The solution, for me, is turn it a bit, let go and wait, then turn it a bit more, etc.

[rwilkey]

I have found that the 8mm BST needs a bit of focus travel - more that other ep's, so it may not be the scope, and OK on the night sky, in fact, incredible.

[Donkeiller]

Tried out my new 8mm BST for the first time last night.

Gives me x188 in my 6SE.

Unbelievably good view of Saturn (despite so-so conditions).

Cassini, ring shadow, banding all crytal clear.

MUCH better than my previous 9 and 7mm EPs that it replaced.

I have the 15, 12, 8 and 5mm- love them all!

[Richardisgreat]

I recently bought the 8mm BST and also i love mine It gives me mag of 150X and 300X when barlowed, I also had amazing views of Saturn and not bad views of Mars I cant wait for Jupiter to come back around I have just ordered the 18mm BST Hopefully it will be just as good.

[nightfisher]

you will love the 18mm bst, they are about the best of the bst`s im still wanting an 8mm and maybe a 5mm bst, looks like im gonna be chucking the celestron x-cel 7mm in the bin

[Caldwell 14]

It should be sound....er thats.! There is nothing wrong with BST's per say ?

[robster]

I'm afraid I'm still having trouble...

I can only compare to a 26mm 2" ep, so magnification will be less, and therefore any loss of focus will be less, but I still can't achieve sharp focus with the BST.?..and this is now a replacement.

I tried focusing on Saturn at about 3am on Sunday morning...did anyone here get a clear view, or was the seeing really bad? I could make out the general shape of Saturn, but that was about it.

The scope has not been collimated since we got it....could this be the issue, or could something else be amiss?

Cheers

[rory]

id say check collimation. could well be the problem,

[Richardisgreat]

yeh id say check the collimation, i use a cheshire collimator.

[wyx]

Maybe try it with a barlow lense? I can get focus on my f5 scope with the 8mm but the focuser almost comes out of its threading. With a barlow it does not require as much travel for me. If it works in the barlow then maybe you just need one of those 'focus extender' thingys. Forgive me I don't know the correct terms as Im pretty new to all this:) , just passing on advice i was given as i had trouble with it at first also. Bare with it tho, the quality over a stock plossel is amazing!

Sent from my GT-I8150 using Tapatalk 2

[knobby]

Is the PDS version the one with the mirror biased for imaging,maybe its a focus travel issue?

Sent from my HD2Droid

[robster]

thanks for the replies.

It's not a focus travel issue - I can find the focus sweet spot, it's just that it's not completley in focus!

Thanks again

Rob

[robster]

could it be I'm using it in a fast scope? (1000mm f5) Are these eyepieces not suited to such a scope?

[rwilkey]

I use mine in a fast scope like yours f/5 f/l 1000mm, and it works fine.

[Donkeiller]

Had a BST 8mm for a month now. Has become one of my most used EPs.

Use it in both my fast (f/6) 'frac and slow (f/10) SCT.

Did you get it from Alan at "Skies the Limit"?

If so give him a ring, he is very helpful