Skywatcher 80ED pro or Skywatcher 150PDS?

[tonedeaf]

as an example

coma cluster (ngc4874 and friends) with an unmodified dslr @iso 800 15x 300s

with ff/fr

the small fudges are galaxies...

(it´s not a perfect image...)

[IanL]

For the smaller galaxies, the longer FL of the 150PDS would be a bit better, but it's still not going to fill the frame of a crop DSLR (e.g. Canon 500D), e.g. M81/82 are not exactly small targets by some standards:

150PDS with Coma Corrector:  http://www.blackwaterskies.co.uk/p/imagingtoolbox.html?BWSFOV=%7B%22version%22%3A2%2C%22fovStyle%22%3A%22ZA%22%2C%22fovYOffset%22%3A0%2C%22fovXOffset%22%3A0%2C%22compDesc%22%3A%22150PDS%20%2B500D%22%2C%22compDisplay%22%3Atrue%2C%22searchTarget%22%3A%22%22%2C%22searchPopular%22%3A%22%22%2C%22gotoRaHD%22%3A148.924277220171%2C%22gotoAddSign%22%3A%22%22%2C%22gotoDecDD%22%3A69.34179992944357%2C%22fovWidth%22%3A1.9%2C%22fovHeight%22%3A1.26%2C%22fovColour%22%3A%22%23FFFF00%22%2C%22fovRotation%22%3A0%2C%22fovAppH%22%3A1.4363200000000003%2C%22fovAppV%22%3A1.4363199999999998%2C%22fovScopeRes%22%3A0.7733333333333333%2C%22searchSurveySelection%22%3A%22P%2FDSS2%2Fcolor-m%22%2C%22gotoRaH%22%3A9%2C%22gotoRaM%22%3A55%2C%22gotoRaS%22%3A41.826532841041626%2C%22gotoDecD%22%3A69%2C%22gotoDecM%22%3A20%2C%22gotoDecS%22%3A30.479745996842734%2C%22ccdWidth%22%3A22.334400000000002%2C%22ccdHeight%22%3A14.8896%2C%22ccdFocalLength%22%3A675%2C%22pixelWidth%22%3A4.7%2C%22pixelHeight%22%3A4.7%2C%22pixelHRes%22%3A4752%2C%22pixelVRes%22%3A3168%2C%22pixelFocalLength%22%3A675%2C%22pixelAperture%22%3A150%2C%22equipReducer%22%3A0.9%2C%22equipRawFL%22%3A750%2C%22equipFocalLength%22%3A675%2C%22equipAperture%22%3A150%2C%22equipCameraVal%22%3A%22%7B%5C%22pixelWidth%5C%22%3A%5C%224.7%5C%22%2C%5C%22pixelHeight%5C%22%3A%5C%224.7%5C%22%2C%5C%22ccdWidth%5C%22%3A%5C%2222.33%5C%22%2C%5C%22ccdHeight%5C%22%3A%5C%2214.89%5C%22%2C%5C%22pixelHRes%5C%22%3A%5C%224752%5C%22%2C%5C%22pixelVRes%5C%22%3A%5C%223168%5C%22%7D%22%2C%22equipCameraText%22%3A%22Canon%20EOS-50D%20%2F%20500D%20%2F%20Rebel%20T1i%22%2C%22equipScopeVal%22%3A%22%7B%5C%22aperture%5C%22%3A%5C%22150%5C%22%2C%5C%22focalLength%5C%22%3A%5C%22750%5C%22%7D%22%2C%22equipScopeText%22%3A%22Skywatcher%20Explorer%20150P%22%2C%22zoom%22%3A2.969076405960179%7D

80ED with 0.85FR:  http://www.blackwaterskies.co.uk/p/imagingtoolbox.html?BWSFOV=%7B%22version%22%3A2%2C%22fovStyle%22%3A%22ZA%22%2C%22fovYOffset%22%3A0%2C%22fovXOffset%22%3A0%2C%22compDesc%22%3A%22150PDS%20%2B500D%22%2C%22compDisplay%22%3Atrue%2C%22searchTarget%22%3A%22%22%2C%22searchPopular%22%3A%22%22%2C%22gotoRaHD%22%3A148.924277220171%2C%22gotoAddSign%22%3A%22%22%2C%22gotoDecDD%22%3A69.34179992944357%2C%22fovWidth%22%3A1.9%2C%22fovHeight%22%3A1.26%2C%22fovColour%22%3A%22%23FFFF00%22%2C%22fovRotation%22%3A0%2C%22fovAppH%22%3A1.4363200000000003%2C%22fovAppV%22%3A1.4363199999999998%2C%22fovScopeRes%22%3A0.7733333333333333%2C%22searchSurveySelection%22%3A%22P%2FDSS2%2Fcolor-m%22%2C%22gotoRaH%22%3A9%2C%22gotoRaM%22%3A55%2C%22gotoRaS%22%3A41.826532841041626%2C%22gotoDecD%22%3A69%2C%22gotoDecM%22%3A20%2C%22gotoDecS%22%3A30.479745996842734%2C%22ccdWidth%22%3A22.334400000000002%2C%22ccdHeight%22%3A14.8896%2C%22ccdFocalLength%22%3A675%2C%22pixelWidth%22%3A4.7%2C%22pixelHeight%22%3A4.7%2C%22pixelHRes%22%3A4752%2C%22pixelVRes%22%3A3168%2C%22pixelFocalLength%22%3A675%2C%22pixelAperture%22%3A150%2C%22equipReducer%22%3A0.9%2C%22equipRawFL%22%3A750%2C%22equipFocalLength%22%3A675%2C%22equipAperture%22%3A150%2C%22equipCameraVal%22%3A%22%7B%5C%22pixelWidth%5C%22%3A%5C%224.7%5C%22%2C%5C%22pixelHeight%5C%22%3A%5C%224.7%5C%22%2C%5C%22ccdWidth%5C%22%3A%5C%2222.33%5C%22%2C%5C%22ccdHeight%5C%22%3A%5C%2214.89%5C%22%2C%5C%22pixelHRes%5C%22%3A%5C%224752%5C%22%2C%5C%22pixelVRes%5C%22%3A%5C%223168%5C%22%7D%22%2C%22equipCameraText%22%3A%22Canon%20EOS-50D%20%2F%20500D%20%2F%20Rebel%20T1i%22%2C%22equipScopeVal%22%3A%22%7B%5C%22aperture%5C%22%3A%5C%22150%5C%22%2C%5C%22focalLength%5C%22%3A%5C%22750%5C%22%7D%22%2C%22equipScopeText%22%3A%22Skywatcher%20Explorer%20150P%22%2C%22zoom%22%3A2.969076405960179%7D

For some wider field targets, the 150PDS might be a bit tight, e.g. M42 or M45:

If you are going really wide field, then you're going to need to do mosaics anyway, and the 80ED would be a big time saver here due to the bigger coverage per frame. (You'll lose a bit around the edges both due to stacking artefacts and also needing to overlap for the mosaic too).

On the plus side effective focal length is not a major issue, 510mm vs. 675mm (with reducer / coma corrector respectively), and weight is not a concern either (6kg vs. 3kg or so I guess), so guiding is likely to be in the same ballpark of difficulty in either case.  The bonus for the 150PDS is the effective Focal Ratio is 4.5 vs 6.4 for the 80ED, so you're going to get more in shorter exposures which is a big help as a beginner.

Personally I am happy with my 80ED, since it requires zero adjustment of the OTA before you can start imaging.  If you're setting up and breaking down each time out, all the tasks you have to undertake add up to a lot of lost imaging time especially if dodging UK clouds and especially when starting out as there is a lot to learn. I don't think there is a bad choice you can make here, either way you're going to get results.

[Gohan75]

Thanks for the very informative info. Hmm alot to think about. I do like the fact that the 150pds has shorter exposure times and i am quite used to collimating reflectors having owned 2. I wonder if the 150pds will fit M31 into its field of view, having said that its only one target of many and like mention no scope is best for all.

Thanks

[PorkyB]

I think all this discussion goes to prove one thing - there is no "one size fits all" solution.

Get both scopes  - you know it makes sense

[Gohan75]

it does make sense! Also, just quickly... are there any other well know alternatives to a skywatcher 150pds? For example are the astrotech 6" F4 scopes good? (If at all available in the UK) and what is an astrography scope? 

[Delboy_Hog]

I do like the fact that the 150pds has shorter exposure times

Can anyone say / give an example of what the difference in exposure time would be, in order to capture the 'same' (as much as that is possible with 2 different scopes) image from an f5 scope and an f6.4ish scope?  If you're taking (for example) one minute subs with the f5, how long would you need with the slower scope, where other variables are the same?  Are we talking seconds difference, or minutes?  I realise that difference will become a lot more significant if you're running much longer subs, but roughly...?

Also following this thread with interest - like you Gohan75 I'm contemplating similar choices!

[tonedeaf]

quattros are real good for AP...someone here on the board uses ist with a reducer and comes to f ~2,8 (if i´m remembering it correctly)

on the other side SW MN190, hell of a scope...the intes ones are out of budget  -> € +5600 for an 200/1200 MN (ok the quality might be very good)

but these are scopes that should be mounted on a eq-6 or higher mount...

regarding the fitting questions (M31 etc) try to dl Stellarium and there you can insert the scope datas, ccd/cmos chips, reducers etc 

and see what effect it will have on some targets....

[frugal]

For the smaller galaxies, the longer FL of the 150PDS would be a bit better, but it's still not going to fill the frame of a crop DSLR (e.g. Canon 500D), e.g. M81/82 are not exactly small targets by some standards:

Wow!, that website is great for comparing scopea and setups. Duly bookmarked for future use.

Sent from my GT-N7000 using Tapatalk

[IanL]

Wow!, that website is great for comparing scopea and setups. Duly bookmarked for future use.

Glad you like it.

I wonder if the 150pds will fit M31 into its field of view, having said that its only one target of many and like mention no scope is best for all.

With careful framing, the 0.85 reduced 80ED plus APS-C DSLR could have been designed with imaging M31 in mind.  The 150PDS would need a two pane mosaic to avoid disappointment:

[laser_jock99]

If you're thinking of going down the Newtonian route (for imaging at least) then also consider the F4 scopes. Collmation and focus are marginally more demanding but if you are confortable with this the payoff in shorter exposure times is worth the extra tuning.

GSO make a nicely built 150mm F4 - though I had to uprate the primary mirror cell springs in mine to stop collimation shifting (I'm not going to 100% recomend this scope at this point in time since I've only used it once in two months since I got it due to bad weather) but early results were interesting.

As for the ED80 there is a place for one of these in your scope collection as well........a guide scope for the Newt!!!

[IanL]

Can anyone say / give an example of what the difference in exposure time would be, in order to capture the 'same' (as much as that is possible with 2 different scopes) image from an f5 scope and an f6.4ish scope?  If you're taking (for example) one minute subs with the f5, how long would you need with the slower scope, where other variables are the same?  Are we talking seconds difference, or minutes?  I realise that difference will become a lot more significant if you're running much longer subs, but roughly...?

Also following this thread with interest - like you Gohan75 I'm contemplating similar choices!

The simple rule is if you double the f-ratio, you need an exposure four times as long to get the same result.  (This is for extended objects like galaxies, nebulae, etc. Whereas for point sources like stars it is just aperture and not f-ratio that matters).

So this graph plots the relative brightness of f/2 vs. higher f-ratios:

You can see that if we go from f/2 to f/4, we will only get a quarter of the light for the same length exposure.  Ditto if you look at f/5 on the graph, you can see that f/10 is only a quarter as bright.

If we call f/5 100%, going from f/5 to f/6.4 you will get approximately 61% of the light for the same length exposure, i.e. you'd have to expose for over 8 minutes to at f/6.4 to get the same as you would in 5 minutes at f/5, or for your specific question a 1 minute exposure at f/5 would need 1 minute 38 seconds at f/6.4.

[Chris]

If your are after a wider field of view for imaging targets like M31 then maybe this should be a Equinox 66mm apo verses the 130pds thread:

http://www.firstlightoptics.com/equinox/skywatcher-equinox-66-apo-pro-ota.html

verses

http://www.firstlightoptics.com/reflectors/skywatcher-explorer-130p-ds-ota.html

The reason I say the 130pds over your current 130 is due to needing to move the primary mirror up the tube to achieve focus with a camera or you need a barlow which as said increases focal ratio. I've owned both and recommend both, especially the 130pds with the 0.9 SW coma corrector which gives 585mm focal length and f/4.5! and the price for a 130pds with a reducing coma corrector is 260 quid!

I'm just putting it out there

Chris

[RikM]

it does make sense! Also, just quickly... are there any other well know alternatives to a skywatcher 150pds? For example are the astrotech 6" F4 scopes good? (If at all available in the UK) and what is an astrography scope? 

The 130P-DS is a good alternative to the 150P-DS and with essentially the same focal length / field as the ED80. I would say though that if you have the budget for the ED80, it would be less hassle and would avoid diffraction spikes which can detract from widefield images, when by contrast, they can enhance some more close-up targets.

[Gohan75]

Bah it seems either type of scope is a good choice. I have a lot to consider. Thanks for all your advise everyone This site is a life saver. 

[Delboy_Hog]

The simple rule is if you double the f-ratio, you need an exposure four times as long to get the same result.  (This is for extended objects like galaxies, nebulae, etc. Whereas for point sources like stars it is just aperture and not f-ratio that matters).

If we call f/5 100%, going from f/5 to f/6.4 you will get approximately 61% of the light for the same length exposure, i.e. you'd have to expose for over 8 minutes to at f/6.4 to get the same as you would in 5 minutes at f/5, or for your specific question a 1 minute exposure at f/5 would need 1 minute 38 seconds at f/6.4.

Thanks Ian.  I didn't realise it was so significant.  Certainly makes it one of the critical factors when considering which scope to get for imaging.

Let us know which one you ultimately decide to go for Gohan...and good luck with the decision!

[peroni]

The simple rule is if you double the f-ratio, you need an exposure four times as long to get the same result. (This is for extended objects like galaxies, nebulae, etc. Whereas for point sources like stars it is just aperture and not f-ratio that matters).

If we call f/5 100%, going from f/5 to f/6.4 you will get approximately 61% of the light for the same length exposure, i.e. you'd have to expose for over 8 minutes to at f/6.4 to get the same as you would in 5 minutes at f/5, or for your specific question a 1 minute exposure at f/5 would need 1 minute 38 seconds at f/6.4.

This has been a truly informative thread and a great read. Good luck with your choice Gohan.

sent from my tablet

[Pete Presland]

as i own both a ED80 and a 200PDS i have found this an extremely interesting thread! i certainly would not want to choose between the two

[ianpwilliams]

I've committed to buying an HEQ5 Pro mount (very excited, can't wait for it to arrive), and up to this point I've been set on buying a Skywatcher Explorer 150P-DS OTA, the intention being that I would do some visual to begin with, and then eventually do some basic imaging, eventually focusing on DSO. But having read endless threads on this forum, and having had the 80mm scopes in the back of my mind also, I do wonder if I should go for the Evostar 80ED Pro instead of the Explorer 150P-DS.

The main advantages of an 80mm scope seem to be:

1 - wider FOV, which can be good for capturing more of individual galaxies without the edges being cut off

2 - easier to work with (no collimation required, less cooldown time etc), so better for beginners (i.e. me)

3 - smaller and lighter, so less stress on the mount

4 - could be used as a guide scope for a bigger scope later on

Whereas the main advantages of the 150PDS seem to be:

1 - bigger aperture (but I'm not sure how much better it would actually be visually, and imaging-wise aperture seems pretty irrelevant)

2 - shorter subs for imaging (but I am a patient man, and with a radio/mp3 player and a pair of binoculars I'm sure I'd be ok with longer subs)

I don't know why but I generally prefer the idea of a reflector over a refractor (based on nothing whatsoever), but if making the choice on the above advantages, then it does make me wonder if 80mm is the way to go.

I did a a bit of messing around on the FOV calculator website comparing the two, and although I know it's only a rough guide, there doesn't seem to be a huge difference in the "zoom" level (not as much as I expected anyway), but really I have no idea of the difference between the two visually. But 150 is almost twice 80 size-wise, so presumably there would be quite a difference. But then surely any decent telescope should give you some great views? Unfortunately I have no way of trying any out, which makes it tough to choose.

In the long term I would be happy to have two setups (one for imaging, and one for visual), but even the size of my visual setup would still have to be limited, due to carrying equipment up and down stairs (so a 250mm Dob would not be an option for example).

[wxsatuser]

I'm biased get the 80ED Pro.

[laser_jock99]

I still think you should get both!

[ianpwilliams]

Yeah but if I went down the 80ED route then I could do imaging, and then I could get a 200P or something later on, which I'm sure the HEQ5 could handle fine for visual, and then I could switch between visual and imaging sessions. The only question really I suppose is how the 150PDS and the 80ED compare visually.

I need a star party!

[Chris]

Yeah but if I went down the 80ED route then I could do imaging, and then I could get a 200P or something later on, which I'm sure the HEQ5 could handle fine for visual, and then I could switch between visual and imaging sessions. The only question really I suppose is how the 150PDS and the 80ED compare visually.

I need a star party!

You can do imaging with both the ED80 and 150pds, the ED80 will be slower so you need to take longer exposures for the same amount of data but the ED80 is a bit less bulky and you don't have to collimate it. You can even do imaging with the 200p as its just as fast as the 150pds but has longer focal length so its better for smaller objects like small galaxies and PN's.

I've used both the ED80 and 150pds for both visual and imaging and I would say that the 150pds is better as an allrounder for the dual purpose of imaging and visual as it will show more deep sky objects than the ED80 and its faster for imaging. I also find 750mm focal length to be an excellent compromise for both widefield and close up

Chris

[PorkyB]

Or get yourself a 130PDS and with the money you save compared to an ED80 you can get yourself a DSLR camera

[ianpwilliams]

It's ok I have money put aside for a DSLR (and everything else that would be needed with it) later on. The temptation is to go with the 150PDS to be honest, but page 2 of this thread makes me wonder, particularly the bit which compares 80ED and 150PDS images, and shows just how tight 150PDS images can be for some DSO's. I would absolutely love to get a photo of M31 one day, but it looks like that could be a real pain using a 150PDS.

[Chris]

It's ok I have money put aside for a DSLR (and everything else that would be needed with it) later on. The temptation is to go with the 150PDS to be honest, but page 2 of this thread makes me wonder, particularly the bit which compares 80ED and 150PDS images, and shows just how tight 150PDS images can be for some DSO's. I would absolutely love to get a photo of M31 one day, but it looks like that could be a real pain using a 150PDS.

If you want a bit more FOV then it sounds like PorkyB's suggestion would suit you best. A 130pds will be very cheap something like 165 quid, its fast for imaging and has a bit more FOV then the 150pds. I've owned a 130pds in the past and sometimes wish I'd kept it, they are rock solid and light and have a great focuser for the money!