I'm new to Ice in Space so I hope this is the right place for the thread.
I want to start doing some imaging and I was going to get an EQ6 mount, but was unsure on which scope to put on top. I already have a 12.5in F5.6 on a split ring EQ mount which is great for visual but useless for imaging ( massive periodic error).
Both the 8 inch F4 and F5 newt' scopes are about the same price to buy, but I hear from other forums that people are having collimation issues with the F4 and I wonder should I give up on the F4 (looks nice in CF) and go to the F5 as a first time imaging person. Even though its 10 inches longer.
I am mostly interested in Neb's and galaxies and will start off with my DSLR unguided and progress from there.
Any advise?
Regards
Bill
P.S The aperture demon keeps telling me to get a 10inch F4.
The 8 inch f/4 will be smaller, so it won't be impacted as much by gusts of wind. Same thing for 10 inch f/4 - you'll need a really good mount.
I saw some good results from a 6inch newt with DSLR recently. That could be something for you to consider. If you're not guiding, you'll need a wide field of view (short focal length) and very short subs.
Thanks for the advise James, I guess unguided is only until I get more gear. Until then I am hoping to get decent 45sec to 60sec subs with a good drift alignment.
if you're getting an EQ6, adding guiding capability will only need a mini 8x50 finder and a guide camera or a modified philips toucam if you're skies are reasonably dark. (small guidescope-easier to get a guide star from darker skies)
you could start off without guiding but will soon see the advantage of guiding as you can increase your exposure time to get details.
From dark skies, you could get some good images with short unguided exposures, but its a bit more of a challenge from near city lights, still very much possible though. I took my first unguided eta pic from my backyard about 20k's from the city with a dslr and an 8" F4.
good collimation is required for an F4 though as well as a coma corrector with the correct spacing for your dslr.
not sure if the F5 will need a CC.
I'd suggest the F4 be it 8" or 10". wider field, more forgiving on tracking errors, quicker exposure and as james mentioned less prone to wind deflections and lighter on your mount.
which OTA's are you looking at?
Hi Alistair,
I most likely will go with the Carbon Fibre 8 inch F4, I'd love to buy the 10 inch, but once I get into adding extra weight it could compromise the EQ6.
As far as brand goes the GSO version is substantially cheaper than the Skywatcher version. I don't know if there are extra goodes thrown in with the Skywatcher or they have better quality parts.
I'll have to ring Sydney and ask the distributor.
I live 40Km Nth of Brisbane so we get really dark nights here, when it eventually stops raining.
It sounds like you have Newt and collimating experience Bill, so that should put you in good stead. Might be worth waiting for comments from F4 Newt owners that image. I find my 8" F5 is a very nice imaging platform, but I do have vignetting issues and would love the extra FOV F4 affords. If you get one of the newer imaging newts with baffles and bigger secondary you should be off to a good start.
I do need coma correction (MPCC) at F5. I believe collimation, tilt and spacing are much trickier to get right at F4 and below. Higher quality focusing gear and adaptors/screw connections may be necessary.
What sort of guiding solution are you contemplating?
My old 12.5in F5.6 is so easy to collimate and its usually just a quarter turn on the primary at the start of a session, hardly ever touch the secondary. I only use the cheshire with cross hairs haven't tried a Laser yet.
My dream guiding system would be a Taurus Tracker III OAG with a Lodestar camera. I like the idea of the 3rd port for an eyepiece, when I have visitors they can have a look without dismantling the image train.
Not sure what to replace the Pentax K100D with, my mind isn't made up between a colour CCD or mono plus filters. It all depends on my patience waiting for all those LRGB and Ha subs to be completed plus darks.
I will have to order a coma corrector, no idea which brand, is dearer better?
I had an 8" F6 and that took literally a few seconds to collimate.
my 8" F4 is a lot more involved but is well worth the effort.
the reduction in exposure duration and the wide FOV are some of the positives.
I just bought a 10" F4 mirror set to build an OTA, so I'm staying with the F4.
with your dark skies, an OAG would work well and you should have sufficient stars to guide. you'd need to account for sufficient back focus though.
I use the baader mpcc and it does the job well provided spacing is correct.
the cats eye collimation tools are very accurate, if not a cheshire and laser might do. a bahtinov mask also helps with focusing as you may not get bright stars to use with live view and the viewfinder can be tricky to look through and focus.
as for colour ccd vs mono, as you said it depends on your patience. mono is a fairly steep learning curve but not impossible.
If your anything like me, and it looks like you will be. Imaging is going to be a slippery slope. You will start with 30 second subs (this was me in August last year) but soon you will push for more, you will move up to guiding. Getting more nebulosity from longer subs you will find that your DSLR is too noisy and you will want a cooled camera.
You mentioned an OAG, this is the stage I am at now. To get an OAG to work on a newt you need the room to put it. To do this I moved the mirror up the tube. This creates more problems F4 is a steeper light cone than F5, If more of the light cone is in the focuser (more backfocus) then not only does the focuser need to have a large internal diameter, but the secondary mirror needs to be bigger.
My newt came stock with a 2 inch 10-1 focuser which has been replaced with a 2.5 inch moonlite motorised one. The secondary was the 70mm "oversized" imaging one, which has now been replaced with an 88mm mirror.
Collimation for imaging is nothing like collimation for viewing, A laser and a cheshire do the same thing eliminate PAE. To properly collimate the scope you need to eliminate FAE aswell, and this is where an autocollimator comes into play.
Quote:
Originally Posted by alistairsam
the cats eye collimation tools are very accurate, if not a cheshire and laser might do.
All in all I would probally have got the F5 if i had my time again, I dont think the trouble of a cheap F4 is worth the payoffs. If I had an endless bank account I would buy an Orion optics AG 8-16. Cheap scopes skimp on all of the bits you need to be precise to get F4 to work well.
If your anything like me, and it looks like you will be. Imaging is going to be a slippery slope. You will start with 30 second subs (this was me in August last year) but soon you will push for more, you will move up to guiding. Getting more nebulosity from longer subs you will find that your DSLR is too noisy and you will want a cooled camera.
Cheap scopes skimp on all of the bits you need to be precise to get F4 to work well.
My 2 cents.
I went through the same slope as well. dslr was too noisy, so got a qhy8 cooled osc ccd, works without darks.
you're right, F4 needs precision but can be tamed.
a low profile sturdy focuser, low profile OAG like the TS-9 or a guidescope, correct secondary, cats eye kit, mpcc, cooled ccd. I reckon that's a workable combo.
Hi
Looks like I will be going that slippery slope and abusing the plastic.
Posted by Pete.M Getting more nebulosity from longer subs you will find that your DSLR is too noisy and you will want a cooled camera.
I guess there is no point in getting an OAG until I get a better camera as the DSLR is the weakest link as far as long duration subs go.
Plus the issue of the size of the light cone after moving the Primary forward to accomodate an OAG. Wow 88mm secondary thats nearly up there with the Ritchey at 95mm.
I think until I replace the DSLR I could use my 9x50 finder off the old 12.5in and get a guidecam for that. That will give me enough exposure time until the DSLR noise is too large. Hoping for 5min subs.
Later a decent focuser with a motor that can be operated from the notebook.
Then later after I buy a new washing machine and keep the Mrs happy, I'll get a decent imaging camera.
I think the most important thing is the washing machine
But you can get very good results with dslr's. since you're imaging from dark skies, you may not need exposures longer than 5 mins depending on the target. you can use dithering and darks to remove noise, as well as capture sufficient subs to increase your snr.
it all depends on your chip temperature as well.
Mike posted a link of some fantastic images taken with dslr's from dark skies, but almost all of them were at ambient temperatures below 20C. It was an uncooled modded camera with the IR filter removed.
as for the OAG look at these dslr's with the TS-9. you need just 9mm. http://www.teleskop-express.de/shop/...daptation.html
But your 9x50 finder should be good enough.
important thing is to start with a decent combo, learn as you go and then move on. I'm learning as well.
Else its a never ending slope until you end up with an AG12 with a large format CCD, a 2000 dollar focuser and a PMX mount or similar !!
I was just reading about how to build a cold box for the DSLR using Peltier technology, it reduces the camera body temp. by 40F, thats something I could do. ( QLD humidity may stop that idea). Probably have to pay for the filter mod though.
Am I right in saying the F4 is supplied camera ready as far as back-focus is concerned ( its advertised as an astrograph). If so the TS-9 may work straight away without any mucking around with longer collimation bolts.
On my 12 inch I had to install a low profile focuser for my DSLR to achieve focus, so I can always use that.
I'm using the stock GSO 8" f4 imaging newt (the non-CF version, with 10:1 focuser and 70mm secondary), together with a MPCC, EQ6, 80mm guidescope/QHY5 and a modded DSLR. Using a laser for collimation. The scope didn't require any modification and is fine for DSLR back focus right out of the box.
Its my first AP rig, and I only bought it in January. I've been very happy with the quality of my shots so far (and i have very dark skies and a modded camera which helps), but i still have a lot to learn and i'm miles away from reaching the limits of my off-the-shelf gear. The stock GSO 8" f4 gets the thumbs up from me. http://astrobin.com/users/rmuhlack/
(all of my astrobin images were captured with the setup described above)
I was just reading about how to build a cold box for the DSLR using Peltier technology, it reduces the camera body temp. by 40F, thats something I could do. ( QLD humidity may stop that idea). Probably have to pay for the filter mod though.
Am I right in saying the F4 is supplied camera ready as far as back-focus is concerned ( its advertised as an astrograph). If so the TS-9 may work straight away without any mucking around with longer collimation bolts.
On my 12 inch I had to install a low profile focuser for my DSLR to achieve focus, so I can always use that.
Bill
Hi Bill,
I'd suggest keeping the camera mods for phase 2. you can still do heaps with an unmodded dslr from dark skies.
There's lots to learn with processing, guiding, accurate goto's, balancing, focuser slop, getting all the software bits working that'll keep you busy.
This image is far from even good, but it was my first dso from a home built mount. it was taken with an unmodded, uncooled canon 1000d from melbourne suburbs. http://www.iceinspace.com.au/forum/s...ad.php?t=73042
so you should get some good results with an eq6, guiding, 8"F4, MPCC and a dslr from dark skies.
IMO, keep your subs to less than 5 minutes, enable dithering, get your guiding, collimation, image train flex controlled and you'll be singing.
As for back focus, its best to ask the supplier. but if its advertised as an imaging OTA, you'd expect it be usable with cameras from the start.
Another member here Justin got a similar setup with the 8"F4 with the stock Bintel focuser and I don't think he needed any mods to achieve focus.
Alistair your absolutely right my time will be spent on on getting better drift alignments, getting software and cables to work. Just viewing objects I could not find from star hopping previously, like Pluto or Neptune.
Your Fork mount looks awesome and solid and the photo of Eta C has a lot of contrast in it for 30 sec's sub frames.
The MPCC will have to wait for phase 2, depending on how bad the images look.
I am sure once I get everything set up I'll be asking more questions.
Those images of Richards look very professional, I can see a lot of time and effort has been spent on them. My favourite is the horsehead, all those different colours.
The coma will be very prominent without the coma corrector, but there is a lens tool in photoshop and other software that can correct it to a certain extent. I think its called the pinch tool or lens tool. can't remember. Not really a substitute but makes your image usable.
don't forget, for a fixed focal ratio, eg. F4, all a large aperture (and hence focal length) does it 'zoom' into the image a bit more (it's still the same 'brightness'), but at the same time brings a whole load of headaches and the costs increase exponentially. The EQ6 is very heavy (head alone is 15kg) and a 10" scope is huge and difficult to mount onto the EQ6. A 6" f4 scope will give exactly the same image, just 'zoomed out' a bit. With 10-14MP camera sensors the norm these days, just crop the image a bit and you'll have the same as a 10" scope from a 6" scope. Yet a 6" on a HEQ5 can be carried together and costs half as much. Baader mpcc work excellent on f5 scopes, not sure about f4.
f4 will need much more careful collimation than an f5, but f5 will need 1.6x longer exposure.
Sorry for not replying earlier, had computer issues.
In the end I purchased the 8in F5 version with the EQ6. I think I was too worried about coma and collimation to buy the F4, plus the F5 had been reduced a lot in price.
I figured the F5 would be a good learners OTA for me, and I am very pleased with the decision now I have had a limited amount of time using it.
The first night I learnt a lot of new lessons, like tripping over cables, must remember to move the little step ladder before slewing or the OTA crashes into it.
I have been carrying the EQ6, tripod and scope rings in and out each evening and yes it is very heavy, lucky I have only 10 steps to make from the garage to the lawn.
I left it outside for a week (removed the scope) during bad weather wrapped up in a blanket and covered with a tarpaulin. Which was Ok everything stayed dry but the ants moved in, so I'm back to carrying again.
I have included my first week of shooting, these are all unguided and no darks or flats, however I did use the camera's noise reduction.
For anyone contemplating buying an 8in F5 newt it is also camera ready and no mod's are required, however the focuser drawtube does extend into the OTA by about 15mm at focus. Not sure whether this a concern yet.
The camera I am using is a K100D unmodified, which is an issue for me as I can't use any of the EOS software around, this means I have to use a stopwatch for exposures.
So where my I have stated 35sec exposure subs they could be anywhere from 30sec to 40sec's. I aimed for 30sec's but fiddling about meant some were longer. May have to buy a DL1100 body.
Can someone tell me the background to IC2602 ( Southern Pleiades), are they stars or camera noise?
