hi this is Graham from Jenham's Astro this video is a follow-up to one I made recently in which
I tried out using a SCT reducer corrector with a Maksutov telescope and if you looked at the
video you see that I had some strange artifacts on the images that I took now I've got a lot of
comments about this video and lots of suggestions for what might be the source of the artifacts
whether it's because it's a reducer corrector whether it's faulty whether there's an internal
reflection uh possibly there's some issue with internal reflection inside the scope for example
baffling and in this video I'm trying to see if I can investigate a little bit what is the actual
root cause so first thing I did was just quickly reproduce the problem the other night and I just
pointed the scope in this setup exactly as you see it here pointed at Venus and just moved the planet
um it's basically like a bright star just moved it around the field of view and it's very easy to
reproduce these arcs these strange arc of light that I saw originally when I photographed apply
these so what I'm going to do here is what I can do I don't particularly want to dismantle
the scope unless I have to so I'm going to look to play around with something that is in my control
that is to say I'm going to see if there's any baffling issues on the scope that easily corrected
so this is the experiment I'm going to do in my garage I've put up an artificial star
on a tripod at one end and I've got the 127 at the other and I've got the reducer
and the DSLR so everything's set up the same way as it was when I took the shots in the first video
and it doesn't seem I can focus on the Stars probably not a great surprise but I'm really going
to just look for any signs of strange Reflections but maybe the same kind of thing that we saw
in the first video um with the nighttime shots
okay so this is without any flocking inside the scope
I can reproduce this Arc it's not great as a demonstration but if I just move
scope a little bit you can see that you get
a ring of light and maybe you shouldn't be seeing that
so now I've put a roll of flocking paper inside the primary battle I've just inserted it and let
the tension in the paper expand it so it's not a permanent installation and now doing
the same thing if I move this move the scope a little bit simulate movement of the artificial
star whichever way you want to look at it you don't see the same Arc of light
on top of the defocused images we did before so perhaps that is a clue I think it may be worth
me trying this out at night and seeing if a primary baffle fix is actually the solution
okay so having put some flocking paper inside the primary baffle I went outside repeated my
test using planet Venus and it made no difference whatsoever still lots of artifacts as the planet
was close to the edge of the field of view and also when it was in the middle which I thought
was quite interesting so if I ruled out the primary as the cause of the problem the next
Target really is is the secondary baffle so to get to that I've had to open up the tube and
I was a little bit worried about doing that but I think touch wood it's okay to do that there is a
a ring here which you unscrew on the end of the optical tube then there is a rubber washer
and it allows you to then take out the corrector so here it is it's a great big thumping lump of
glass it weighs 840 grams and certainly explains why cool down times on Maks are longer than they
are on SCTs so there it is I've marked the orientation of the corrector I'm not really
sure whether they are particularly matched when they're put together in the factory but I've
marked the angle so that hopefully I can put this one back at the same position as I took it out
so you can see as a mirrored dot on the inside that serves as the secondary
so having a closer look at the baffle hopefully you can see if I just bring it up to the camera
you can see that the inside of the baffle whilst it is black is quite reflective it's I guess a
conical shape like this but still it seems possible that this reflection is the cause
of our problem so what I'm going to do is I'm going to paint this carefully with some matte
black paint and then see how we get on um whether that removes the artifacts or not
so I ended up using a bit of black self-adhesive flocking paper on the inside of the secondary and
when I compare the view just looking into the secondary when it's been covered compared to
what I had before it seems like there's a major difference in terms of reflection so I went back
outside looked at the planet Venus again now I know the image is Overexposed but it I don't think
it matters for the experiment but when I move the planet into the edges of the field of view I saw
exactly the same effect it made no difference whatsoever the only difference perhaps I could
perceive was that when the planet was right in the middle I didn't see any reflective sort of
ring or effect around the planet which I did see once before so maybe that was down to the baffle
so I think I've drawn a bit of a blank here really other than eliminating the baffle as the source
of the problem so for now I'm going to park the investigation. if I see any other way forward if
someone lends me another one of these reducers or I don't think it's this particular one but I if I
see another way of investigating it I'll uh I'll make another video but for now I think I've got
to conclude that it is either the this particular unit I think it's probably unlikely or it is the
fact that I'm trying to apply a correction when one isn't necessary the the reduction that this
unit gives me is clearly bringing uh the light code more of the light going into the field
of view onto the sensor of the camera and it's revealing something that otherwise probably is
hidden from the camera in its normal native focal length so thanks for watching sorry I haven't been
able to conclude hope it's been of some interest nonetheless if you haven't subscribed to Jenham's
Astro please click the link and look out for more Astro videos this and thanks for watching