hi this is Graham from Jenham's Astro in this video I'm going to do an experiment I'm going
to try using this Celestron F 6.3 focal reducer corrector which is normally designed to be used
with a Schmidt Cassegrain telescope like this one I'm going to try and use it for Imaging with this
a 127 Maksutov telescope now if you think that might be of interest and you haven't already
subscribed to Jenham's Astro then please click the button and let's see how this experiment goes.
okay so back to basics before we actually do any of the tests but what is this device so the 6.3
reducer corrector from Celestron now there's a bit of controversy a lot of discussion online
at least about what the corrector element of the name suggests now a lot of people say that it is
actually correcting for coma so that the sort of cone-shaped effect that you can get with stars
as you go off axis should be reduced into one of these and other people say well maybe it's
actually a flattener device so that's going to change the field curvatures so that the image
is in focus across the whole focal plane now devices like scopes like schmidt cassegrains
suffer from coma as well as a lot of field curvature whereas Maksutovs have much less,
they have a flatter field naturally because they use a different shape corrector lens
than the one in the SCT so basically if I don't get into what's actually true about whether this
is correcting for coma or flattening what I'm trying to determine is if I use a device like
this designed for this type of telescope in one of these is it going to introduce more problems than
it solves in terms of optical quality now because I'm not probably smart enough to fully understand
all the ray tracing and all the octal elements that are in play here I'm simply going to try it
and I'm going to try using a digital SLR so basically you're going to take the 127
I've already attached an adapter thread because as you might have seen in my short video I've had to
adjust that so that it takes the SCT thread after that I'm going to put the reducer on
and then I'm going to use my Canon 700d now this is a cropped sensor camera it's an APS
C camera sensor so it's not a full frame sensor which is a factor we'll come to a
bit later on but nonetheless we we're going to have a look and see what kind of images we
get when I use this scope with the reducer and the camera versus using it without the reducer
so one more thing before we get started it's always worth mentioning that spacing is important
when using any kind of reducer corrector flattener device so in this case Celestron recommend that
you should have a distance of 105 millimeters between the lens at the back of the corrector
reducer and the sensor within your camera so I'm using a t adapter which is a model 93633 which is
the standard T adapter that you've used to connect up DSLR onto the back of your SCT so when I use
this adapter with the reducer it's all worked out quite nicely so that you have the right separation
basically I think there are 44 millimeters of distance between the flange on the front
of this EOS DSLR and the censor chip and then the the t-ring is adding around 10 millimeters
and then the adapter is adding just over 50 millimeters so if we add all that together
it gets this to the 105 millimeters now I'm going to start with this I'm not going to
vary that although I'm aware that changing that spacing will adjust the effective focal
reduction that we're getting but I'm just going to use a setup that's recommended
using the standard adapter no extra Spacers or anything else like that so okay that's the
setup let's have a look at what we get with this arrangement with and without the reducer
okay so the first thing I did was take the camera and the telescope outside during the
day and I took a frame with the camera just looking up at the up at the sky and you can
see here that it's evenly illuminated this is a crop sensor camera but basically it's all
the same level of Illumination throughout the frame and then I fitted the reducer
and you can see around those Corners there's quite a lot of vignetting they're not full
illumination of the field of view this is what you expect with a reducer function it's squeezing
the output from the back of the telescope into a smaller angular range in order to allow you
to see what's outside of that range but it means that you don't get full illumination
so this is something to look out for when we get onto looking at night sky viewing
so for the reducing function the most obvious target is always the moon now the moon itself
fits quite nicely into the field of view of this telescope and the camera setup we've got
around about just over half a degree vertical angular size on on the frame so I can fit the
field of view the whole the whole moon no problem without any reducing but if we do fit the reducer
you can see the moon is now surrounded by it much more blackness lots of space
and obviously in this case you can't really see you can't tell the difference between the black
background and a loss of Illumination but the reducing function certainly works pretty well
as for correcting so basically what I did here is I put the the scope onto my
Vixen AP Mount and it took a series of 30 second frames ISO 1600 just to see
what the image quality was like and I pointed at the plighties so Messier 45.
pretty early on when I started to look at a couple of the subs I noticed some strange effects you can
see down here that especially if you look down at the the lower right or the upper left some strange
arcs of light eliminating from these Bright Stars it's not visible from the star in the middle of
the field but this was something strange going on so even though we can fit the whole of the
Pleiades into the field which is good for reducing something strange was happening I was a little
worried that my reducer corrector was actually faulty so what I did then was I decided to fit oh
I should say actually that you can fix this sort of field illumination aspect to that problem you
can see around the edge of the vignetting you can fix that with flat frames pretty easily so there
you go but it doesn't detract from the fact that we got these strange arcs so what I did was then
I took my five inch my C5 Celestron C5 and put the reducer straight onto the back of that to see
whether these artifacts were visible with the SCT and you can see here that we fit the Pleiades into
the field of view slightly different image scale because the focal length of the two telescopes a
little bit different but we don't see any strange effects and after the 30 exposures we're starting
to see a little bit in their velocity coming through so this told me straight away that
the reducer seems to work okay but when I fit it onto the Mak some strange things are happening
so then I already have the C5 on the mount so I moved on to another Target so I pointed the
scope at the Orion Nebula and took a shot with a C5 and the reducer corrector and yeah pretty
nice image it just lets you see more of the frame as you might expect and quite
good rendering of the Stars a little bit of uh aberration at the at the edge so it's not
perfect but it works pretty well with the C5 but then went straight back to the 127 and
you can see the bright star again near the edge here on the right we've got the Arc of
some sort of distorted light now I'm not sure whether this is an over correction because like
I said you don't need to correct the the Mak's field and we are doing that with the
reducer corrector but certainly I don't like that artifact over there over on the right
and then finally took the 127 back to its native focal ratio to F12 and obviously we are
shrunken in here to seeing less less sky if you like but we're not seeing any artifacts so
that's what we get just with 127 on its own
so my conclusions from this experiment which only uses one telescope , well one Mak and one SCT and
it uses one reducer corrector so I would say that for Imaging the answer probably is no that
Distortion is was pretty awful I think the fact that it worked on the C5 suggests that it's not
a faulty reducer and it's just the fact that we're trying to use an inappropriate device with the Mak
so I don't think this is a way of making your F12 Mak much quicker and using it for Imaging
as for visual well vignetting was isn't too noticeable you're not too sensitive to
it in the way that you are when you when you're taking long exposure with imaging
um we didn't see and it couldn't see the arcs visibly that we picked up when we we took those
longer Subs but still the Stars weren't pinpoint I really didn't like them there
was there was some Distortion throughout the field of view and they weren't nice pinpoints
so what I'd say in summary is that if you've got a reducer corrector already for your SCT then use
it I think it's a great device and certainly with my C5 and Evo 8 it is really nice it's a lot of
fun and you get you do actually get a benefit from it so definitely for visual with an SCT
and probably for Imaging as well I haven't done it I recommend the reducer corrector
but if you've got a Mak certainly like it's 127 I think it should stick with its native focal
ratio put up with this narrow field of view because when you use it in that configuration
the field is wonderfully sharp and you get lots of contrast so I hope it's been useful video um
it's following on from the videos I've seen from my Astro friends like Garnet Leary so I hope this
is built on that and given a few of you some ideas if you've wondered whether you could do
a miracle transformation on your Mak into a faster scope so I would say a little bit of caution there
so thanks for watching and please look out for more videos from Jenham's Astro bye for now