That first scope question

[anuvid]

I'm in the depths of Kent and appear to have reasonable sky from a pollution perspective (though it's no Mohave desert here). My son is majorly into an ipad app that lets him identify objects in the sky (he's 7 by the way) and I had set my mind on a GoTo scope. In fact I'd settled on a Celestron 4SE for £ 399. Mainly becaus eit was GoTo, and also it was capable of taking my wife's DSLR if he wants to take photos. My only concerns are that the motor may not cope with a Nikon D70, and also that the high f figure will apparently scupper my chances of seeing DSOs. I'm wondering what realistically I can expect to show my sone other than the moon, the gas giants, and blobs that are galaxies ? I'd love to go spend time with local astronomy groups but he's so eager that I'll probably settle for the 4SE if no better ideas are forthcoming. I did also see that there was a Celestron 127 recommended on here, but the difference between the two wasn't immediately apparent to me. Any help appreciated. Also if anyone knows of a specialist scope shop in Kent please let me know. I'm in Sittingbourne.

[JamesM]

Aperture effectively translates as resolution and is why you will see the phrase, "aperture is king" abound on much equipment advice. Now GOTO is great but the snag is often this, that if it has to come out of the same budget as the scope itself, it will often mean that the scope size (aperture) will be compromised and so you can easily end up will a situation in which the GOTO will take you there, but you haven't got much 'scope' to make it worth the effort. In fact on some deep sky objects, the effort will be a complete waste of time. The system will take you to some 12,000+ objects but is the scope up to seeing them?

I would see the 127, having more aperture as heading in the right direction and its focal length will make it ideal for moon and the planets and some DSO's. All scopes can receive a webcam to take images of the moon and planets because being so bright, they don't need long exposures which translates into accurate tracking. You collect the frames from the video, stack the best of them using free software to construct a composite image. Imaging deep sky objects (DSO's) is another ball game because they are faint, far away and will require the level of accuracy found in a mount such as a HEQ5 and upwards, which alone is almost twice your budget. So a webcam would be as far as your imaging aspirations could go for now. The 'F' ratio you see stamped on the side of the scope is of more interest to images who require a 'fast' or lower numbered scope and is why scopes great for observing are not necessarily ideal for imaging.

My concern for you in choosing a scope from which you will be able to build on your son's enthusiasm, is that there maybe some disappointment. I would imaging the application your son enjoys will illustrate the objects using colour images - there is very little colour when it comes to deep sky objects in particular. Resolution or detail, as indicated above comes with aperture and I personally would start at around 8" as being the size when you start to look at some details in the objects rather than just seeing a general fuzzy shape. To that end, my first recommendation will be for you and your son to attend a public viewing session organised by your local astro club/observing group to go and see exactly what these objects look like for real in order that you can test his reaction to what he sees. By looking through different scopes, it will also give you some idea of how different the view looks, the size and set up times of some of this kit. A dobsonian scope is by far the best value for money as all the money goes into the scope itself without the toys, but it will mean finding the objects manually which isn't difficult but takes a little practice and it will also mean moving the scope to manually track the object which is fine when using low magnification but as you ramp that up the image will move quicker through the eyepiece.

So overall I would advise to try before you buy, (at least to manage expectations) aperture is the key but will necessitate a compromise within the budget, imaging via webcam restricted to moon and planets and last but by no means least, don't rush the research, the stars aren't going anywhere!

Hope that helps

James

[anuvid]

James, it's magnificent advice. As I mentioned I'm just not sure that he has the patience to wait for the opportunity to go to viewings. I think I should probably explain to him that the kind of scope that I'm willing to invest in initially will really only be good for large solar objects, without much detail. Out of interest how much would I have to pay for a scope of the capability required to start collecting enough detail to make using a DSLR worthwhile ? The other reason that GoTo seemed a good idea was the constant tracking. A motor moving the scope to follow the object does open up some possibilities even with webcam imaging I assume. Thanks for taking the time to reply so thoroughly, I really appreciate it.

[StevieDvd]

Do a search on Nexstar 4SE on the forum to see what images are being taken with the scope.

When I was first looking I had the 4SE and 127 on my list, the supplier said the difference in aperture between the two was not worth worrying about but that the mount on the 4SE was better and could take a 5" scope later if needed.

Factor in to your budget a dew shield, barlow, 12v portable power pack. If your son is into his Ipad you can get a Skywire adapter so he can use his ipad to point & go directly (there is a wireless version as well).

[anuvid]

Steve, thanks. I have a feeling that I will be tempted b ythe 4se with a view to moving to something more substantial next bonus from work !

[Odd Dob]

The issues with that scope are

1. it's a Mak type design, so it's a "slow" scope as you've already identified. That makes it difficult to view DSO. (My 180 Mak is hopeless at it, but it does depend of the exact focal length of scope and eyepiece).

2. It's a alt-az mount, not an EQ mount. DSLRs are usually used for DSOs. An alt-az mount is of no use for this, as over the time it takes the camera to do a decent enough exposure, the frame would have rotated around. You need a EQ mount so that the whole frame maintains orientation during tracking.

You can get goto EQ mounts, but that tends to put up the price a bit.

[anuvid]

Odd Dob, is there an out of the box scope you'd recommend along those lines ?

[Odd Dob]

Generally, equatorial mount means faff and hassle to set up, so I don't think there's an "out of the box" solution that I can think of.

You could get quite straightforward set ups for planetary photography (using e.g. that scope in the OP and a webcam) but using DSLRs you need to worry about polar alignment, tracking guiding, etc. It's a world of pain

[anuvid]

Sounds like I should abandon the DSLR and DSO world and start off with some basic planetary stuff, and letting my boy try to spot the men on the moon, and their buggies :-) 4SE is still looking llike a good starter. I imagine it's resale will be reasonable too if I decide to up the stakes within a couple of months.

[pvaz]

The problem here, in relation to DSLR photography, is not the 4SE but the mount (tripod etc) that is supporting it.

For DSO photography you need long exposures to make up for the low light emitted by this objects. Problem is a long exposure on a moving object causes ghostly images. As the Earth rotates DSOs seam to move. To null the Earth's rotation you need to use an EQ motorized mount. This mount haves an axys you align paralel to the Earths axys and then it rotates at the same speed but opposite direction, to nullify that movement. Alt-Az mounts such as the one on the 4SE don't account for that rotation.

[umadog]

Honestly, forget the DSO DSLR photography. It's not like terrestrial photography, it's an involved and time-consuming process which is effectively a different hobby from visual observation.

GoTo may not be a bad idea if you have a child who wants to see objects NOW and doesn't want to wait for 15 minutes whilst you identify something. The only problem is that he may not be terribly impressed with the views through a <6" scope. You should be ok if you make sure his expectations are very well calibrated. Buy yourself a copy of Turn Left at Orion (which has eyepiece impression drawings) and show him what to expect and what the corresponding photo looks like from the internet. If you don't do that, he may well be disappointed when he finally looks through the eyepiece. Note that even with a larger telescope the views may not be significantly more impressive. It all depends on the object and the light pollution. The path to enjoying the views is to know what you're looking at. How big is it? How far away is it? What is it?

[anuvid]

All good advice again. Many thanks all.

[JamesM]

Anuvid, to answer your reply to my post, as Umadog has made clear above I would forget the idea of using your DSLR. On your budget, a webcam is the way to go and you will be able to produce good images of the solar system (NOT the sun - just in case!). A webcan can take a vast number of exposures very quickly so that there is effectively no need for tracking. It's DSO imaging that requires very accurate tracking hence the expensive mount leaving the scope or the camera as secondary considerations to this primary piece of kit.

If you are after a scope with sufficient aperture (8") that will perform well on planets AND will show some detail on deep sky objects, which allows you to move the scope around the sky using electronic controls (great fun for kids) and which has tracking that can help maintain the object in the eyepiece, which not only aids focusing but allows time for different observers to come to the eyepiece without the usual scramble, then the Skywatcher Skyliner 200P Flexitube Auto might meet your needs. However, it is slightly more than your original budget costing at around £455. I couldn't find any other scope of that size that also tracks. You could buy the same scope without any electronics for a fair bit less but then that would make the whole set up manual - which I guess you don't want. I have no idea if this tracking scope can be upgraded later into a GOTO, I suspect probably not but even if it were possible, the extra cost would make having all the 'toys' from the start far more attractive. Now its easy for me to spend your money and for some reading this, the amount would represent quite an investment compared to your original choice of scopes mentioned in your post. It is for that reason that I would suggest you give First Light Optics a ring to discuss it over with them. Being astronomers themselves, they will understand your objectives and help you fine tune your choice.

As said in my earlier post, all the specifications and numbers won't mean a thing unless you have established your own bench mark from which to measure whether they will meet you and your son's expectations. If your son doesn't have the patience to go to an outreach event, I believe he will show less patience in the subject as a whole when he eventually gets to see the difference between what is visually possible compared with that of imaging as seen on his phone app.

Again Hope that helps.

James

[anuvid]

James, another thorough and considered response that I think is excellent. £ 455 is not out of the question. I'm having a chat with my son to see if any telescope this side of a South American mountain range is going to provide the results he wants. Given how excited he got with his binoculars earlier I think he's pretty realistic for a 7 year old.

[Ags]

I have a 4se and it is a capable scope for viewing planets, the moon and some brighter DSOs. I have also attached an ST80 scope to the mount for some basic messing around with imaging of DSOs. However i would think that any sort of imaging (planetary or DSO) is a bit too involved for a seven year old.

You can look at my threads to see my ill-judged efforts at 4SE deep sky imaging... ;-) If you search the forum you will see some impressive planetary imaging examples posted recently by other 4se owners.

The 4se is a fun little scope that can do most things in a modest way. It is light and portable and not intimidatingly expensive.

[anuvid]

Thank you. I think it's probably the right scope for my son. I've just seen a 5k Celestron that I want :-)

[Ags]

One of the reasons I picked the 4se was because I wanted to share the view with young relatives. You can get the eyepiece down to kid height (and you can view sitting down, which really improves the views), and the tracking keeps objects in view while the young astronomer fumbles about with the focus.

I was torn between the 4se and the 127 mak but went for the 4se in the end because of the slightly better mount. If I did it all again I would be seriously tempted by the 127 instead.

[anuvid]

What is it about the 127 that makes you wish you'd gone that way ? I had the same question, but elsewhere on the forum someone mentioned that their (reputable) supplier said that the difference between the two is on paper only, and not significant in the real world. Anyone got experience of this - it may be new:

Celestron SkyProdigy 90 Computerised Telescope

Celestron SkyProdigy 90

[pvaz]

The amount of light gathered is proportional to the area of the primary lens. 127 will have 69% more area then 100mm (~4") so images will be 69% brighter.

It won't make a huge diference in bright objects, but it may be the diference between resolving some individual stars on globular cluster or just see it as a blob. In theory it will always show more, in practice it depends on the object you're seeing. Some will show visible improvements some will look the same.

When it comes to aperture, bigger is better.

[Ags]

Well, with my maths I get 55% more light in the 127 over the 4SE - so you would see stars more or less half a magnitude fainter.

If you are looking at a small, detailed object like Jupiter, you will get a 25% boost in angular resolution. If the 4SE resolves an area into 16 'pixels', the 127 would resolve the same area into 25 'pixels'.

You will also be able to use slightly higher magnifications on planets with the 127 because (1) it gathers more light, so the image will be brighter at any given magnification, and (2) the exit pupil will be larger at any given magnification. This isn't quite the same thing as (1) because with a larger exit pupil imperfections in the eye like floaters are less apparent.

The difference in aperture between the 4SE and the 127 is exactly the same (25%) as the jump between my ST80 and my 4SE. I've compared those scopes closely and the difference in light gathering is significant.

SkyProdigy 90? Too small. Too expensive. It's got lots of electronics to save you literally 3 or 4 minutes of setup time, at quite a price. For the same money, get a NexStar 6SE.

[pvaz]

Yeah, redone the math using 101,6mm for the 4", got 1,5625 ratio so about 56% increase.

Must have typed something wrong the last time.

[anuvid]

I really appreciate everybody's advice which has been extremely balanced and fair, and mostly nobody has ridiculed my newbieness. I'm pleased to report that I visited my local store (which I didn't know existed), F1telescopes.co.uk, and the gentleman gave me great advice the upshot of which matched most of yours. Don't bother with the 90 - alot of money for lots of gizmos but little optical value. 4SE or 127, and despite my love or burnt orange I've bought a 127 SLT and the powertank. The powertank is charging and I hope the skies clear tomorrow for lunar observation day or whatever it is called.

He did show me a webcam and software for about £ 120 but I've decided that'll wait. I'm excited and will post my first impressions as soon as we've had a play. Thanks all again, and have a great weekend.

[Ags]

Enjoy the new scope!

[anuvid]

Thanks Ags. Don't know if I made the right choice, but I made A choice - I hope my next one is mre informed.

[pvaz]

Regarding the webcam, a modded phlips SPC900 (or SPC880 with firmware upgrade) will do exactly the same as the celestron one that goes around for 100, with just a fraction of the price. If I recall correctly my SPC880 was 20, s/h already moded including the nose piece 1,25" adapter.

You can use sharpcap to capture the video and registax to stack, both good and free software.