As a starter telescope: Skywatcher 150PDS or Celestron C8-s

[NeilFawcett]

OK, given the desire for some general observational astronomy of both planetary and deep sky (eg: nebula) objects, and to take some photographs to. Which would be best suited for these jack of all trade requirements (ignoring price)?

- a new Skywatcher 150PDS with EQ5Pro goto mount, or a second

- a Celestron C8-s - http://www.celestron.com/astronomy/telescopes/celestron-c8-sgt-xlt.html

From generally looking around the C8 seems the better option? Anything else I should be aware of?

Am I correct in saying:-

- Although the 150PDS would be larger, it would lighter? ie: Would the Celestron be significantly heavier to move?

- Would the mounts basically be the same between the two scopes?

- The Celestron would require less complex collimation?

- The Celestron would require less maintenance generally. ie: MIrrors aren't exposed etc.

The unit would need to be transportable as it would need to be move easily in/out of the house etc, and the scope taken off the mount for storage etc.

Thanks for any advice.

[michael.h.f.wilkinson]

Big upvote for the C8

The Celestron C8 OTA is a featherweight amongst telescopes, weighing in at just 4.7 kg, lighter than the 150PDS OTA, and much easier to mount. I have had my C8 on Great Polaris mount for nearly 17 years, so it is more than just a starter scope. It is a great all-round visual performer, getting excellent views of planets and over 600 DSOs so far. I can take it on holidays in the car (along with the missus, her shoes, kids, tent, more shoes, cooking gear, more shoes ), and can transport it to darker locations when needed easily. It is also very good on planetary photography (see avatar).

If ever I get a bigger scope, I am keeping this one as well, just as (LARGE) travel scope. The C8 is simpler to collimate, and holds collimation excellently (I rarely if ever need to tweak antything).

I have added a 2" visual back so it will accept 2" EPs, and that has been a great bonus, allowing me to get a much wider FOV (1.34 deg max).

[Tinker1947]

The Celestron isn't really suitable for DSO's its a bit on the slow side( High F Number) , 150PDS is a lot faster and much better for DSO's you will need a good mount for the 150PDS a HEQ5 or if the wallets will stretch a NEQ6, Collimation is really quite easy, just needs a couple of attempts and your wonder what all the fuss was about, the Mirror on a Newt is right at the back of the tube, it will be years between cleaning and there easy to remove and replace....my NEQ6 gets carried out every session the 250PDS i have is easy to carry and mount....

[crazyjedi]

Hi

Yes the SW is pjysically longer (but narrower in diameter) and yes it is a fair bit lighter.

I think the mounts are similar. I'm not sure about the collimation of an SCT but my newt (I have the SW 150) is easy enough).

On the last point not many people do any more in the way of mirror maintenance other than collimation. The only time a mirror would need anything more would only be in extreme and rare circumstnce.

I know the SW 150 is a good scope generally but the C8 will be equally well made.

Someone may well dissagree with me on this but I think that SCT's are good for planetary work and imaging but not as good as newts for deep sky stuff. The difference won't be enormous though. The SCT will be a fair bit slower and more forgiving on your EP's but they are both great starter scopes.

The C8 will have more light grasp than the SW 150 but will be heavier to handle/transport.

They'll both be very good scopes for you which ever you choose

[NeilFawcett]

The Celestron isn't really suitable for DSO's its a bit on the slow side( High F Number) , 150PDS is a lot faster and much better for DSO's you will need a good mount for the 150PDS a HEQ5 or if the wallets will stretch a NEQ6, Collimation is really quite easy, just needs a couple of attempts and your wonder what all the fuss was about, the Mirror on a Newt is right at the back of the tube, it will be years between cleaning and there easy to remove and replace....my NEQ6 gets carried out every session the 250PDS i have is easy to carry and mount....

So if we consider two examples:-

- Viewing or photographing the moon or Jupiter. Surely the C8 would win here?

- Viewing or photographing the say the Orion Nebula (M42)?

I'd be looking at both of these on an EQ5 pro goto (or equivalent) mount. As long as these are stable enough and allow for a DSLR and possibly an autoguide I'll be happy.

And the opinion seems to be although the C8-s is heavier than the 150PDS, it's not enough to consider it?

[michael.h.f.wilkinson]

So if we consider two examples:-

- Viewing or photographing the moon or Jupiter. Surely the C8 would win here?

- Viewing or photographing the say the Orion Nebula (M42)?

I'd be looking at both of these on an EQ5 pro goto (or equivalent) mount. As long as these are stable enough and allow for a DSLR and possibly an autoguide I'll be happy.

And the opinion seems to be although the C8-s is heavier than the 150PDS, it's not enough to consider it?

To start with the last: That opinion is wrong. The C8 weighs 4.7 kg, the 150PDS 5.9kg.

- The C8 wins on Jupiter both visually and photographically

- The C8 wins on M42 visually, but not photographically (with a 0.63x compressor it gets better, but not ideal, and I have made a few shots guided manually on film (donkey's years back)).

I have looked through both a 6" Newtonian (with smaller central obstruction than the 150PDS), and found the image in the C8 better on planets in terms of detail (even if the contrast might have been a shade lower). For visual work on DSOs, the C8 wins hands down, because focal ratio is irrelevant for visual work. If I look through an F/8 Newtonian with an 8mm EP or through an F/5 of the same aperture with a 5mm EP, the image on the retina is the same (bar the slightly larger central obstruction of the F/5 which makes it slightly less suitable visually). The fast focal ratio does have an advantage on wide field views, but objects more than a degree across are few and far between.

Neither set-up is ideal for DSO photography. Here we must think mount first. An HEQ-5 is considered the minimal mount for DSO AP. On this you could guide a small, fast refractor for preference. The 150PDS might work (though 750mm focal length requires precise guiding, but the frac has the advantage of not needing collimation. Also, in DSO imaging speed is more important than aperture. Here the 150PDS is clearly ahead of the F/10 SCT.

[DirkSteele]

The Celestron isn't really suitable for DSO's its a bit on the slow side( High F Number) , 150PDS is a lot faster and much better for DSO's

Should clarify that the slowness is only relevant for astrophotography. Visually it has no impact (other than reducing the maximum field of view you can obtain).

[crazyjedi]

The SW 150 should be ok on an EQ5 but I'd have thought that the C8 would not be stable enough on an EQ5.

Generally SCT's are not used for deep sky imaging. Nwets are pretty good for DSO's but the serious deep sky imagers mostly seem to use fast apo fracs (which cost £££££££).

I guess it depends how serious you are about imaging. Both scopes are great starters. If you want to start tinkering with imaging very soon then perhaps the SW 150 is a more flexible imaging platform to cut your teeth at astrophotography before saving up for something more dedicated to imaging.

[michael.h.f.wilkinson]

The SW 150 should be ok on an EQ5 but I'd have thought that the C8 would not be stable enough on an EQ5.

Generally SCT's are not used for deep sky imaging. Nwets are pretty good for DSO's but the serious deep sky imagers mostly seem to use fast apo fracs (which cost £££££££).

I guess it depends how serious you are about imaging. Both scopes are great starters. If you want to start tinkering with imaging very soon then perhaps the SW 150 is a more flexible imaging platform to cut your teeth at astrophotography before saving up for something more dedicated to imaging.

The EQ5 is a clone of the GP mount I have. No problems for the C8, even with the added weight of a 16x70 finder

[crazyjedi]

The EQ5 is a clone of the GP mount I have. No problems for the C8, even with the added weight of a 16x70 finder

Is the C8 solid enough to image with on this mount?

[michael.h.f.wilkinson]

Is the C8 solid enough to image with on this mount?

The mount is or isn't solid enough for the scope, not the other way round.

In this case: Planetary: fine, DSO: not. the EQ5 is not recommended by serious DSO imagers anyway (not even for my little frac). Of course, with patience some people do get decent results. I have some nice slides of M42 taken through the C8 with focal reducer (at F/6.3), freezing my nadgers off on the roof of my parents' place on Fujichrome 400 pushed to 800 ASA, and manually guided for 25 minutes or so. NOT recommended

For the 6" scope, using the EQ5 is seriously undermounting it for DSO work as well. For visual and planetary, it is fine. I am going to get either an HEQ5 or an NEQ6 for my DSO imaging set-up in the future, but still retain the C8, as a very portable, yet very powerful visual scope.

[michael.h.f.wilkinson]

BTW, either set up is excellent for the simplest form of DSO photography: Piggyback. Just attach a DSLR with a fast, short telephoto and use the scope to track. With good polar alignment, I have made 15minute exposures which showed no field rotation or guiding errors up to 400mm telephotos.

[NeilFawcett]

BTW, either set up is excellent for the simplest form of DSO photography: Piggyback. Just attach a DSLR with a fast, short telephoto and use the scope to track. With good polar alignment, I have made 15minute exposures which showed no field rotation or guiding errors up to 400mm telephotos.

Sorry, don't quite follow that. If the mount isn't sufficiently good for simple DSO photography with either scope, how would it fair better with a DSLR mounted on the scope too?

I'm surprised the 150PDS (or even the C8) on and EQ5 pro cant be used for DSO photography? ie: ten x 90 second exposures for example? Surely it can cope with that?

[michael.h.f.wilkinson]

Sorry, don't quite follow that. If the mount isn't sufficiently good for simple DSO photography with either scope, how would it fair better with a DSLR mounted on the scope too?

I'm surprised the 150PDS (or even the C8) on and EQ5 pro cant be used for DSO photography? ie: ten x 90 second exposures for example? Surely it can cope with that?

It's the focal length that counts. Guiding errors are magnified by long focal lengths. Consider a 200mm telephoto. These can be used hand-held easily, even if a tripod would help. A 400mm is still OK, but more difficult to hold. Now try a 750mm (the PDS) or a 2000mm (the C8). The camera shake would ruin photos on all but the sturdiest tripods. The same holds when tracking: in a 200mm lens, a guiding error of a few seconds of arc would not be seen, in the 2000mm they become 10 times larger, and may be most annoying. Maybe the mount can handle 10 90s exposures, but that is very short in terms of DSO photography. Many people use hours of data to get good signal to noise.

They other issue is that telephotos are fast: I used my 200mm at F/3.5 or 4, and my 85mm at F/1.4 or 2.0. The latter requires 25x shorter exposure to get the same brightness in the image than my C8 at F/10. The image is of course smaller, but for big objects like some comets I took, the result is fine (the slide is much better than the scan of a print, BTW)

[NeilFawcett]

Maybe the mount can handle 10 90s exposures, but that is very short in terms of DSO photography. Many people use hours of data to get good signal to noise.

OK... Please bear with me here as I'm trying to understand all this being a noob...

1) So the C8 will natively be more "zoomed in" than the 150PDS. Hence the slightest shake/wobble will be amplified?

2) Looking around there seems to be people taking DSLR photos with the C8s on the standard CG5 goto mount? Seemingly without any serious hassle from the mount itself? Or is there an issue I'm missing?

Apologies for any ignorance on my part!

[michael.h.f.wilkinson]

In terms of imaging, the C8 is more zoomed in, it is a higher power lens. Visually, this is not an issue, as it depends on the magnification (and therefore eyepiece) you are using. Besides, the compact format of the C8 means less torque (and weight) is put on the mount, so the overall shake may be less.

As I said before, DSO imaging can be done, but it is not the best performer in this field. You can (and people do) guide a small refractor on the mount. Most DSO shots through the C8 are taken with a focal reducer, which makes it a 1260mm telephoto at F/6.3, which is OK, but according to much better imagers than I am requires an NEQ6 class mount to work reliably. I think that is the key phrase. If you do not mind messing up quite a few shots (at least now you do not waste film ), you can do DSO imaging from an EQ5. It is just that an HEQ5 or CGEM(DX) is a lot more stable. They also cost more money, of course.

A wise approach in my view would be: start out visually, then move to planetary AP (which requires a web-cam, but not much more in terms of investment), and try unguided piggyback if you already have a suitable DSLR, followed by guided piggyback, and then get a small ED refractor (like the SW 80ED) and guide scope to do DSO imaging. The EQ5 may be good enough for you. You might even get it to work with the C8. If not, you can always upgrade the mount later.

[michael.h.f.wilkinson]

BTW, there is this:

A very nice example of what a 150PDS on a GP mount like mine (i.e. similar to EQ5) can do in skilled hands. Really worth a look.

[crazyjedi]

The mount is or isn't solid enough for the scope, not the other way round.

In this case: Planetary: fine, DSO: not. the EQ5 is not recommended by serious DSO imagers anyway (not even for my little frac). Of course, with patience some people do get decent results. I have some nice slides of M42 taken through the C8 with focal reducer (at F/6.3), freezing my nadgers off on the roof of my parents' place on Fujichrome 400 pushed to 800 ASA, and manually guided for 25 minutes or so. NOT recommended

For the 6" scope, using the EQ5 is seriously undermounting it for DSO work as well. For visual and planetary, it is fine. I am going to get either an HEQ5 or an NEQ6 for my DSO imaging set-up in the future, but still retain the C8, as a very portable, yet very powerful visual scope.

Sorry that is what I meant. Got my words in a muddle