Stacking filters Issue - Is it lens flair or me?

[Fozzie]

Afternoon,

I've been grabbing some quick sessions recently with the 4"F11 2" Diagonal and 1.25" Ep's, primarily on the moon and Jupiter with the 9mm SLV.  I have a semi apo filter and neodymium filter which I quite like to stack on these objects, or should I say used to..  

Recently I've been seeing what looks to be a lens flair right through the middle of EP, which is really off putting, I don't notice it without, so im assuming its the filters..

Now I think its relevant but I've been observing from home (mainly because of the young one, some time constraints and early morning starts), which has about 8No street lights within a hundred yards or give or take (yes 8 of the pesky blighters, you can stop laughing now) so LP is very high and generally there is a lot of stray light around, but I have shaded an area so I don't think its light between my eye and the EP..

Could all the stray light be causing the flair or is the stacking of the filter, or is it just lack of dark adaption, or do I need to see my optician??

your thoughts are welcome as always!

Thanks

Fozzie

[John]

Filters can introduce additional glare and light scatter and using more than one of them even more so. Having used 3 of the SLV eyepieces I'd suspect the filters before the eyepiece. The SLV's seem to be very good when it comes to controling light scatter.

[Fozzie]

Filters can introduce additional glare and light scatter and using more than one of them even more so. Having used 3 of the SLV eyepieces I'd suspect the filters before the eyepiece. The SLV's seem to be very good when it comes to controling light scatter.

Agreed, I don't for one minute think its the SLV... in fact im just in the process of running a side by side with the 9mm xcell lx (I know it has a bigber FOV) and the 9mm SLV knocks the socks of it in respect of this... when I finish (going to run them through a F5 80mm too) i'll post my thoughts.. 

thanks

Fozzie

[John]

Agreed, I don't for one minute think its the SLV... in fact im just in the process of running a side by side with the 9mm xcell lx (I know it has a bigber FOV) and the 9mm SLV knocks the socks of it in respect of this... when I finish (going to run them through a F5 80mm too) i'll post my thoughts.. 

thanks

Fozzie

I'll be interested to read that Fozzie

Personally I feel that Vixen have produced a really excellent eyepiece in the SLV. It's not exactly cheap but neither is it outrageously expensive. The performance and comfort of the ones I've used are right up with the best.

[spaceboy]

I'm probably wrong but is this not normal when using a refractor and diagonal on an almost full moon ?  The moon is a big bright object and when its reflection sits on a diagonal mirror your eyepiece is only focusing on a small proportion of that image with a lot a moon light still wanting to get in to the eyepiece. I don't think the problem spans across all magnifications and it is only at certain angles but I have come across similar flaring in almost all of the refractors I have owned. Either that or I have had scopes with some terrible baffling ?

[nicoscy]

Have you tried the views with a single filter? This should tell you instantly if it's the double filter stack...

[Fozzie]

To be fair I've seen it with a single filter, definitely with both, and both times its been on an 80%+ moon... could it be as spaceboy describes, too much light getting through, wonder if a 1.25mm diagonal would make a difference?

[nicoscy]

So, apparently it is not the filters. Especially not the Moon & Skyglow which really increases contrast on the moon.

Not an issue of dark adaptation as especially for the Moon and major planets, you should not really dark adapt.

Try wrapping something around the dew shield to extend it further out (some piece of plastic or whatever is handy) and see if that helps.

[Fozzie]

Thanks Nicos, will give it ago... and see what affect a lower mag has... just generally have a play, see what happens!

[Northern Soul man]

HI Ya Fozzie,

             I think that your placing the filters on the base of the EP - wonder if you have tried placing the filters on the inside of the diagonal which sits inside the scope to see if you have the same problems with scatter - this would move the filters to the other side of the diagonal away from the underside of the EP.

Not sure what format the filters are that you have and I've not used the apo filter,  but if its anything like the UHC - S filter I have - it tends to have a nice reflective surface on it - same with the O III's, but if you can it would only take a minute to place the filters on the "inside" of the diagonal away from the EP - I do this a lot with my variable polarisers - I place one on the "inside" of the diagonal where it slides into the scope and the other at the base of the EP, then I just rotate the EP to give the variation of light through put.

Not sure if this will work, but would be worth trying all the same.

Paul

[Fozzie]

I'm going to try this also... The filters are 1.25 so I'll use my smaller diagonal, should have any issues with field stops at unless I go over 25 mm or so (i think!?)

Thanks

Fozzie