190MN v C8 SCT

[BlueAstra]

I've been reading great things about the 190MN when used with CCD cameras, and it certainly has me tempted. It has a 190mm aperture, f=1007mm and works at F/5.3. I presume its well corrected so you don't need a focal reducer to cover a DSLR FOV. With my C8 SCT & 0.63FR & DSLR I'm operating at F/6.4 with a 200mm aperture, f=1280mm, and the coma is corrected. Is the correction of the 190MN that much better than the C8 & FR combination? Or is the slightly faster focal ratio the benefit? I would like to be sure I get a substantial (£900 worth!) benefit before progressing.

[SteveL]

The MN190 is very flat across the entire field, and nearly 4 times faster (f/10 versus f/5.3), but be aware that the MN190 field of view is much larger than the C8, its a longer and heavier tube, and the dovetail can introduce some flex into teh system if you are side-by-side guiding.

[narrowbandpaul]

agree entirely with steveL

for imaging, given those choices it would be the 190 easily. Dont have to think about it!

[MartinB]

I think an SCT is a great long focal length choice. The spacing of required to achieve F6.3 is huge, 110mm gives me F7 with my 10" Meade. Flexure in the optical train can be a problem esp with a large chip such as with a DSLR.

The SCT has greater flexibility than the 190MN esp if hyperstar compatible. However, whether you are going down the long focal length route or hyperstar you will be getting into seriously challenging imaging.

An 8" SCT is more manageable than the 190MN in terms of weight and bulk. The MN is heavy and long which will challenge an EQ6 if there is any wind around.

The image shift when focusing an SCT is a pain as is mirror flop when crossing the meridian, neither are insurmountable obstacles.

If you are hankering after more than 1000mm focal length than an SCT could make sense otherwise I think you would be better forgetting an SCT and comparing with a 120mm refractor.

An 8" SCT with a replacement focuser and an off axis guider can be an awesome set up especially if used with adaptive optics but we are talking significantly more £££ than a 190MN

[BlueAstra]

The MN190 is very flat across the entire field, and nearly 4 times faster (f/10 versus f/5.3), but be aware that the MN190 field of view is much larger than the C8, its a longer and heavier tube, and the dovetail can introduce some flex into teh system if you are side-by-side guiding.

With the 0.63FR I'm working at F/6.4 with the C8, so its not too different. The MN190 has a slightly shorter focal length, so I guess with the DSLR the FOV will be slightly larger (1.3 v 1.0 deg). The F ratio is about a half stop greater so I could expect ~ 20% more light (?) for extended objects.

I'm using an EQ6, which I think is rated at about 25kg max load, so should be OK. I use an OAG so don't have the extra weight of another guide scope.

I think really its based on whether you consider the MN190 is capable of producing better quality images than the C8 & FR setup, takinging into account that you get a slightly larger FOV and a slightly (?) brighter image.

[narrowbandpaul]

If the image quality of the 190 isnt higher than an SCT I will eat my hat.

I know there are good SCT's out there, but I havent met one yet and have been soured by the 16" pile of c**p in the uni observatory....

Ally and I recommended the 190 to a friend without hesitation...

In fact if I was in the market for a good imaging scope without spending megabucks then I would buy one.

[Whippy]

If the image quality of the 190 isnt higher than an SCT I will eat my hat.

I know there are good SCT's out there, but I havent met one yet and have been soured by the 16" pile of c**p in the uni observatory....

Ally and I recommended the 190 to a friend without hesitation...

Have you actually used a Mak-Newt Paul? I wouldn't like to think that you're making recommendations 'without hesitation' based entirely on other people's experiences....

Tony..

[MartinB]

I know there are good SCT's out there, but I havent met one yet

Seems a bit harsh.

http://stargazerslounge.com/imaging-deep-sky/100222-ngc-4565-needle-galaxy.html

http://stargazerslounge.com/imaging-deep-sky/96468-horsehead-ngc-2023-a.html

http://stargazerslounge.com/imaging-deep-sky/94713-crab-nebula-oiii-finally-added.html

I'm very happy with my 10" Meade LX200R. I have no grumbles at all with the quality of the optics - FWHMs <2 arc secs, completely flat field across an APS chip at F7 using an AP focal reducer, no star distortions at the edge of the chip. It is easier to use with a decent crayford focuser. Best to use with off axis guiding.

Provided you understand the foibles inherent in the design an SCT can certainly deliver the goods. Greg Parker seems to turn out good stuff with his hyperstar system and Damian Peach doesn't seem to have any complaints.

I now also have a MN190 but haven't given it a whirl yet. I think it's like trying to compare dogs and cats

[narrowbandpaul]

Yes tony...I havent used one, but I see the excellent results that are ROUTINELY achieved, plus it has a flat field, and is fast, so I dont have any hesitation in recommending it. It is also reasonably priced. My friend has it and is very happy with it.

Martin, firstly I said there are good ones out there.....which means that I know that good ones exist. Which is true. Also I havent met one yet, means that personally speaking, I havent seen one of the good ones.

Also you have the 'R' version which gives you the flat field. You take good images with it. A conventional SCT is pretty bad for field flatness, at least for the ones I have used.

An SCT can be made good...but its not good as standard. You need the focal reducer, you need and external focusser.

An LX200R with external focusser will work well. But I have only ever used the standard LX200 with moving mirror focussing. Which is horrible to use. Again, a personal experience, and opinion I am entitled to.

oh, Tony, I have used a Intes Micro Mak newt, 6". Its very nice. Virtually a 6" apo in performance. Havent imaged with it though. Havent specifically used the MN190 either.

[Whippy]

So you have not used one, but you'll recommend it because it because you've seen a few decent pics and your friend has one. Hardly actual experience with one is it? I'm very well aware of what Mak-Newts are capable of, I've owned two and yes, there's plenty of decent images taken with one, but as I couldn't reach focus with either of mine with a camera, I can't recommend one purely because I haven't used one for imaging.

As Martin and others has routinely shown, decent images can be taken with a SCT, as you can with any scope design providing you're aware of their faults. So why can't you recommend anything else without hesitation?

Tony..

[narrowbandpaul]

i recommended it to the friend who now has one.

Why not anything else? Well price for a start, he was buying mount and guidescope with his budget. He could have gotten a small apo for the same price, but then he has a small aperture, slower F number, and definitely needs a flattener.

It is a scope made for imaging, which gives both speed and aperture.

What other astrograph can you get which offers better performance without going towards FSQ's and epsilons?

any newt needs flattened...

SCT's a bit too bulky and slow for an HEQ5, and too long a focal length for starting out with....

so with say £1000 what would you recommend that will out perform the MN190.

dont recommend anything you havent used. Some people dont like...

[Coco]

My 190Mn was ordered today from FLO....

It will be interesting how it compares with my sadly but replaced beautiful Meade 127 APO...

Go for it BlueAstra

Guy....

[michael.h.f.wilkinson]

I do not think the question was about a choice between 8" SCT and 190mm Mak-Newt, given you have no scope in this size class. Rather, the question is on whether or not to upgrade.

The Mak-Newt is a great scope by all accounts, but is it the scope to go for to upgrade from a C8 or similar? I have not imaged with my C8+focal reducer in many years, but I wonder whether the Mak-Newt will blow it away. If you are upgrading, the question really is what you are gunning for: an all-rounder or a specialist. If you are a pure deep-sky imaging person, the MN is a great scope, but it will not provide a quantum step in imaging, I think. The MN is no slouch on planets, I gather, but the stability of my C8, due to its short tube when tracking/ imaging planets is great. I can also easily chuck it in the back of even a small car and head off to a dark place beyond the reach of light pollution. This is harder with the MN. If you want something in the 1000mm focal length range, you will need a greater bump in speed than 6.4 -> 5.3.

Does anyone make an 8" F/4 APO with flattener?

[Whippy]

so with say £1000 what would you recommend that will out perform the MN190.

dont recommend anything you havent used. Some people dont like...

Well I wouldn't put a MN190 on a HEQ5 for starters, far too heavy for that. Nor would I think one as a beginners scope either as it has a longish focal length, it can be tricky to collimate and it's a bit of brute to move around. I wouldn't get them to spend all their money either in case they don't like it.

On a HEQ5 for beginner taking up imaging? Easy, ED80 all day long. And yes, I've got one . Under a grand? Not sure, probably an ED120 on the proviso there's an EQ6.

At the end of the day, you can recommend what ever you like based on what you read and what you think but there's no substitute for experience which you've got very little of (and in the case of the MN190, actually none). Quote theory and anecdotal evidence all you like but until you've actually spent some time with your own kit and worked through it's kinks and quirks I find it laughable that you can sit there and recommend anything.

Tony..

[Deneb]

Well I wouldn't put a MN190 on a HEQ5 for starters, far too heavy for that. Nor would I think one as a beginners scope either as it has a longish focal length, it can be tricky to collimate and it's a bit of brute to move around. I wouldn't get them to spend all their money either in case they don't like it.

Tony..

Would have to agree with you Tony... No way for a HEQ5, but regarding the performance between two scopes - SCT or MN190, two different beasts Sir, Not to say that the SCT would give you bad result, but my money would be on the MN190... for imaging, Just my 2p's worth..

Nadeem.

[narrowbandpaul]

well he is doing an astronomy degree, so maybe he likes astronomy? he said about 2K all in, so I told him (as did NGC2403) what he should get for that.

With your refractor recommendation he would also need a flattener, which would need to be a) well designed, the spacing between lens and sensor would need to be very accurate. Which is a pain in the ***.

Yes tony, you are right. I can recommend anything I want. I will continue to do so. You may feel that I am useless at astronomy, have [removed word] all experience, but others do come to me for advice. Particularly with image sensors. But wait, I dont have a CCD camera, so how the hell can I recommend one? I wish my PhD in image sensors would tell me how image sensors worked! Oh wait it does! So I can recommend CCD cameras based on the science that goes on to make an image, more specifically to reduce the image quality. I know enough about CCD Cameras to recommend one, and I know more about the different vendors, and the lies they propagate than most.

Yes I dont do much imaging just now, but let me say why. Not that its any of your business.

Firstly, some of us live in Scotland, where we get far less clear skies. Also it is frequently cloudy even though BBC predict it clear. Secondly, my mount was an EQ6, to which I would have to upgrade before I could even get close to the image quality I demand. Then there is even attempting imaging in the UK. With so few clear skies I couldnt do as much as I want to, and hence not get the image quality. And I dont want to fork out for the kit I want as a) cant afford it, am saving money to train to fly.

I have used my WO66, with EQ6 and SLR to shoot several objects over the course of a year, all with one hour of exposure. Even with that, I dont get a very good image. Well it is below my standards anyway. Kinda gutting when you spend several thousand on a setup and get poor results. So I will be upgrading, but it will be a significant upgrade, which I cant at the moment.

and your quite personal attack is rather disappointing to have come from a super mod. Why are you preventing free speech and personal opinions? Doesnt seem like something someone should do. Especially if they have power.

[MikeWilson]

Could the MN190 sit on a HEQ5 PRO if one is not guiding, or using a finder-guider?

[Deneb]

Mike, you have to understand the OTA is 10kg in weight, minus the finderscope, tube rings & dovetail weight, especially when you fit a ADM Dovetail to the scope from what I know it might be even heavier then a 10" newt. where people have had those on a heq5 pro for visual only from what i've heard.. What concerns me more are those 1.75" legs over the 2" legs offered on the EQ6's. Maybe if the HEQ5 Pro's had better legs they could support larger ota's for imaging.

Nadeem.

[MikeWilson]

Hi Nadeem,

Yes, I think you're right there. I didn't realise the EQ6 had thicker legs - I expect it does make a difference although the HEQ5 PRO is quite a solid mount (at least for the kit I've got on it); the 150P on my HEQ5 PRO is about half the weight of the MN190, but I also have rings and an ST80 piggybacked on it which is why I thought a finder/guider + MN190 on HEQ 5 PRO might be a workable compromise.

I think I might get a 200P DS in the nearish future - and then look for a second hand EQ6 and MN190 when the time comes.

There's plenty of time for all that later, right now the limiting factor (as already mentioned) is our terrible weather!

[sixela]

With my C8 SCT & 0.63FR & DSLR I'm operating at F/6.4 with a 200mm aperture, f=1280mm, and the coma is corrected.

Not really. AFAIK, all these correctors correct for is a part of the field curvature, but there is quite a bit of coma at the edge of the field in SCTs and that doesn't get corrected. The baffling in a C8 is also more aggressive than in most imaging Mak-Newts, so when you use a reducer the vignetting at the edge is't negligible in the C8 either (of course that helps to hide some of the coma in the corners too ).

[sixela]

so I could expect ~ 20% more light (?) for extended objects.

46% more light per sensor area. (6.4/5.3)².

[Ant]

SCT's a bit too bulky and slow for an HEQ5, and too long a focal length for starting out with....

Sorry Paul, thats rubbish!

I have just bought a C9.25 and I'm mounting it on a HEQ5. It is within the weight limit of the scope and from the limited time I have had with this combo performs well.

I mate has used a C9.25 and small WO refractor side by side on the HEQ5 and it still worked well.

I wonder have you had a C8/C9.25 HEQ5 combo?

Ant

[Whippy]

Yes tony, you are right. I can recommend anything I want. I will continue to do so. You may feel that I am useless at astronomy, have [removed word] all experience, but others do come to me for advice. Particularly with image sensors. But wait, I dont have a CCD camera, so how the hell can I recommend one? I wish my PhD in image sensors would tell me how image sensors worked! Oh wait it does! So I can recommend CCD cameras based on the science that goes on to make an image, more specifically to reduce the image quality. I know enough about CCD Cameras to recommend one, and I know more about the different vendors, and the lies they propagate than most.

Yes I dont do much imaging just now, but let me say why. Not that its any of your business.

Firstly, some of us live in Scotland, where we get far less clear skies. Also it is frequently cloudy even though BBC predict it clear. Secondly, my mount was an EQ6, to which I would have to upgrade before I could even get close to the image quality I demand. Then there is even attempting imaging in the UK. With so few clear skies I couldnt do as much as I want to, and hence not get the image quality. And I dont want to fork out for the kit I want as a) cant afford it, am saving money to train to fly.

I have used my WO66, with EQ6 and SLR to shoot several objects over the course of a year, all with one hour of exposure. Even with that, I dont get a very good image. Well it is below my standards anyway. Kinda gutting when you spend several thousand on a setup and get poor results. So I will be upgrading, but it will be a significant upgrade, which I cant at the moment.

and your quite personal attack is rather disappointing to have come from a super mod. Why are you preventing free speech and personal opinions? Doesnt seem like something someone should do. Especially if they have power.

I never said you are useless at astronomy, what I've said is I find it laughable that you recommmend kit 'without hesitation' without any actual experience of owning or using it.

Make all the excuses you want about clouds (it's the same everywhere), throw your PHD at me, I'm not really bothered. What I am bothered about it is people being given bad advice on SGL. You can't sit there saying SCT's are bad because you haven't seen one, yet there's thousands of happy users of them doing visual and imaging with them. That's opinion you're dressing up as fact and it's wrong.

I'm also finding it laughable about how I'm preventing free speech yet in the same sentence, no-one from the mod team is allowed to voice how they feel. I don't have power (it's always a team effort here) and even if I did, I certainly wouldn't throw my weight around like you're claiming. If you don't want to get upset over someone pulling you up because you're spouting rubbish then I suggest you stop spouting. Easy eh?

BTW, If you want a personal attack, I'm happy to give one if you want.

Tony..

[MartinB]

Boys please, spats make unpleasant reading for most, fun reading for those with malicious intent and no useful info for Blue Astra.

Please all go and have a nice cup of tea.

[Jamie]

Can i please ask everyone to take a minute to think about what and how they are posting. This is all getting a bit out of hand.

I am not about to get into a debate about who said what to whom. Just give it a rest guys!!