Help needed with first scope...

[SkyExplorer]

Hi,

I've been interested in astronomy for a while now and decided that it's time to get my first scope so here I am making my first post.

The requirements I have set myself are:-

• I'm looking for something that is easy to use and not too large, thus enabling me to easily move it outdoors and does not require too much maintenance
  
• I'd like the aperture to be a minimum of 120mm
  
• I'd be initially observing the moon/planets and would like to progress to brighter DSO's.
  
• If the bug for observing bites I would like to start astrophography of planets, maybe with a webcam later this year.
  
• I have a budget of £400.
  

So far I've narrowed it down to the following:-

• Sky Watcher EvoStar-120 refractor (either on EQ3-2 or EQ5)
  
• Sky watcher Explorer-150P\200P reflector
  
• Celestron Omni XLT 120 refractor
  
• Celestron Omni XLT 127 SCT
  

Currently I'm temped by the refractors as they seem to require the least maintenance and offer a good image, however I am not sure how bad the colour aberration is with them so would be keen to hear from anyone with one of these.

I guess I'd like a nice simple scope that will enable me to nurture my interest and allow it to grow rather than get a very large scope that needs a lot of maintenance and setup time, and so will then end up staying packed away somewhere as it takes too long to setup/collimate.

Any views/suggestions welcome.

Thanks for all your help.

[crepitis]

I own a 4" refractor and the Skywatcher 200 reflector and both are great scopes which compliment each other well, but if I had to choose one over the other I would go with the 8" reflector , aperture rules as the cliche goes

[Bizibilder]

Hi Firstlight and welcome to SGL.

When starting out, as you have researched, keep it simple and buy something that can easily be upgraded. Aparture is king for smaller scopes and you get much more of it with a reflector rather than a refractor ( big lenses are MUCH more expensive than mirrors!). I would go for the 200P on an EQ5 mount. This comes in at just under budget and gives you a decent sized scope on a good mount that is easily upgradeable to either motor drive or all the way to computerised goto.

I bought one of these myself and have to admit that I am very pleased with it. I intend to motorise the mount as soon as I have it set up in my new observatory!

Would you need portability? If so the 200P is portable by taking the tube off the mount and, if required, the mount off the tripod. Each piece is easily transportable. If you are going to move it around much KEEP the packing! It will be much easier to carry it around in a car if you are off to a dark site. If at home it keeps it dust and dirt free while you set up!

Collimation is NOT a black art - mine came perfectly set up but I have had a play with it - you may need a third arm to reach the screws, but then that is what Mrs Bizibilder is for!!!!

If you are interested in photography don't go down the Dobsonian route - you will HAVE to have a motor driven equatorial so you might as well get the basic EQ mount to start with.

Hope this helps.

[SkyExplorer]

Hi,

Thanks for the replies Bizibilder and crepitis.

The scope does not have to be too portable, I will be storing it indoors so I will need to be able to take it into the garden without too much trouble. So I guess I can take the scope off the mount and move them seperately if need be.

So with a reflector if you are carefull when moving it then it will not require too much maintenace?

So this may seem like a silly question, but what is the advantage of achromatic refractor over a reflector? For the same price you can buy a reflector that is nearly twice the size (aperture wise) and thus will allow much fainter objects to be seen? If i have that right?

Thanks

[Astro_Baby]

On the requirements you set out I'd get the 200 on the EQ5. It will give you biggest bang for the buck for observing and potentially web cam imaging.

I dont do imaging so I cant comment on the imaging issues. Collimation on a 200 is pretty stable. Mine is bumpred around on country roads for use and is seldom put out of kilter so long as your reasomably careful.

Get a Cheshire collimator and its really not as hard as you may believe. All scopes need some maintenance - its parts of the hobby really.

[Saturnalia]

Do you have an astronomy club or society nearby...?

If so, it would be well worth a visit - they usually welcome potential new members and will be happy to let you have a look through some refractors and reflectors so you can see the difference.

[SkyExplorer]

Thanks for your reply.

It sounds like the scope to get is the Explorer 200P on an EQ5 mount (my first thought before looking at refractors).

I do have a club nearby and will be in contact with them shortly as I'm sure they hold events etc that I'd like to go to, it will also allow me to meet with people with a similar interest.

Cheers

[jimhaleysscomet]

You could always get the Skyliner 200P on a dob mount (easier to move inside and out) and then later add an EQ5 mount for photography. It would save you money at the start.

Or start with the 200P on the EQ5 and build a dob base for it (again, to make it much lighter to get inside and out). The EQ5 is not an easy lift object.

And another "OR" .... start with the Skyliner 200P dob, take short exposures with it to debug your photo equipment, and then add a very solidly mounted 80mm scope for long exposure photography. Again, this would cost no more in the long run than a EQ5 mounted 200P and would be MUCH easier to move around.

For visual use.... aperture is everything and a 250P dob might be transportable enough for you (especially a flex tube model) . For long exposures the tracking mount becomes much more important.

[pvaz]

... what is the advantage of achromatic refractor over a reflector? For the same price you can buy a reflector that is nearly twice the size (aperture wise) and thus will allow much fainter objects to be seen? If i have that right?

An achromatic refractor means it haves color aberration. When the light goes through a lens it's divided and the colors meet at different points causing false color on bright objects (there's more to it but thats the basic idea). You need a refractor with corrected lenses (ED or APO) to avoid this. Mirrors don't have this effect on light so you get no color aberration (a reflector is equivalent to an APO refractor), on the other hand if you go for a fast reflector (under f/6) you may see other problems as coma (elongated stars on the edges) this can be solved with high quality EPs, coma correctors, or by getting a reflector >f/6.

The price difference is based on the cost in manufacturing of mirrors vs lenses not on visual advantages.

[SkyExplorer]

Thanks for your feedback.

I think I'll go for the Explorer 200P, it's a fast scope (f/5) so hopefully should not be too bad with coma and has a lot of aperture for the money.

I guess the EQ5 mount can be computerised should I wish to use it to take images in the future and thus allow longer exposures? (been looking at the review in this months sky at night mag regaring cameras )

I think I'll go to my local shop and see how easy it is to move the EQ5 mount and the OTA.

Thanks for the info on achromatic refractors pvaz. However I'm not sure now why these exist! They have colour aberration as you stated so are not ideal for photography, for visual use you can get a var larger reflector for the same money. Why would a achromatic refractor be recommended?

[pvaz]

Thanks for the info on achromatic refractors pvaz. However I'm not sure now why these exist! They have colour aberration as you stated so are not ideal for photography, for visual use you can get a var larger reflector for the same money. Why would a achromatic refractor be recommended?

APOs are very expensive; refractors are more compact then reflectors and some people don't want to collimate so I guess it fills a market segment for beginners that have their mind set on a refractor but want it at low cost.

The chromatic aberration ain't that much of a problem for visual use, only bright object (planets and moon) bring it out. Some people use filters all the time and they change the colors. The atmosphere itself affects the light, so I guess in the end it's always a mater of personal taste and how deep is your wallet.

[Astro_Baby]

Its a good idea to see a 200 on an EQ5 or an HEQ5. They are quite big beasts. They dont look that big in a field but when you have to lug one about they start to look a lot bigger believe me.

[SkyExplorer]

I saw it in the shop before and was quiet surprised by the size of it. But it's just a hollow tube so should not weigh too much - I hope!

Is it worth getting a polar alignment scope to go into the mount when I buy the scope? I guess I'll have to align it everytime I use it so will it make a big difference in reducing the setup time?

[SkyExplorer]

Just had a word to local shop and they said the scope may need collimating fairly often and a customer who had bought a 200P said he need to collimate it during observing as just moving the scope during observing caused it to need collimating. :-o Not sure if had something wrong with it but is this representative of a reflector?

Thanks

[LukeSkywatcher]

As far as i can tell.....the larger the mirror (primary) on a reflector is, the more often it needs collimating. A once off initial full collimation is a must. After that it is just a slight tweak of the primary or secondary due to the effects of transporting it to your observing sight. I seriously doubt if any scope need full collimation before every use unless you are transporting it long distances strapped to the roof of the car over 6" deep potholes along country lanes.

Refractors do not need collimating. The are collimated in the factory. DONT be put off by the maintainance needed on reflectors. After the initial collimation (which seems scarey until you just do it), it should just need a tweak here and there. The biggest (perhaps the smallest) issue with reflectors is dew,frost on the mirrors. With refractors you simply wipe the lens with a lint free cloth........(basic solution).........or use a hairdryer,heated dew straps etc.

If i were you i would go for the SkyWatcher Explorer 200P.

As i am SURE you already know....................."Apeture is king".

[pvaz]

I would not advice wiping any lens/mirror, it will still be a bit foggy (like when you wipe your car wind shield) and you risk damaging the coatings. To get rid of dew use a small portable hair drier and give them a little heat. It's fast and effective and unless you stick the hair drier to the lens at max heat, there is no risk of damaging it.

[LukeSkywatcher]

I would not advice whipping any lens/mirror, it will still be a bit foggy (like when you wipe your car wind shield) and you risk damaging the coatings. To get rid of dew use a small portable hair drier and give them a little heat. It's fast and effective and unless you stick the hair drier to the lens at max heat, there is no risk of damaging it.

SORRY. I must not have made myself clear. CERTAINLY NEVER wipe the mirrors of a reflector with anything. You will run the risk of scratching the coating. Let it dry naturally or use a small hair dryer.

ALL i meant was that refractors are pretty robust pieces of equipment and a simple BUT gentle wipe of the objective lens with a sort cotton cloth or lint free cloth will not damage it. ALWAYS be sure to look at it before hand and if you see any grit on it make sure to blow it off before wiping. I suppose avoid wiping at all costs is the best way to go.

[LukeSkywatcher]

I've had my reflector out for 2 weeks now in sub-zero temps and have not had a single dew,frost,condensation issue with it. I just know however that the summer months will be a pain in the backside.Dublin suffers HUGE moisture problems during the summer months. My 90EQ and bins are saturated within 20 mins.

[SkyExplorer]

Thanks for all your replies.

Before i take the plunge, can I assume the consensus is to go for the 200 reflector over the 120 refractor?

What can I expect to see with the 200 reflector that I could not see with the 120 refector? Been looking around and it seems hard to find any information about this. I guess its hard too compare with photos as they are not representative of what the eye sees (unless the exposure is set to 1 second or less ).

Once again thanks.

Steve

[Astro_Baby]

I have a 200 on an HEQ5 its collimation does need an occasional tweak but rarely and mines bumped about in a car quite a bit.

The most likley reason the person you mention has for needing constant collimation is the mirror retaining screws are too slack. Some scopes seem to come from the factory like that and its VERY easy to fix. The other likley causes are over fussy collimation, cheap and nasty laser collimator providing odd results or the collimation lock nuts arent done up.

A 200 in good order with its mirror clips firmly and correctly set shouldnt need much in the way of collimation unless its very roughly handled.

Anti dew for a refelector can be as simple as a dew shield and a 12v hairdryer.

[pvaz]

Well the biggest difference is on the light gathering ability.

Objects brightness is measured in magnitude. The lowest the magnitude number, the brighter the object is. The larger scope will allow you to see objects fainter as it haves 2.77 times the primary area, which means an increase in 177% of light.

On practice lots of other things interfere, mainly light pollution. As an example, an experienced member here, that lives under light polluted skies, told me he can't see some galaxies I see with ease and his scope is a 16" (300% more light gathering power then my 8").

So lots of things come into play. If you live under heavy LP then a more portable scope may be better to take to a dark site.

[Saturnalia]

Anti dew for a refelector can be as simple as a dew shield and a 12v hairdryer.

You can also make your own dewshield to save money - even thick cardboard rolled up with gaffa tape to hold it together works or for a more permanent version, use an old foam camping mat and cut off what you need to roll one up.

Stick the edges with gaffa tape or get some velcro strip and glue onto each edge - using Velcro means the dewshield 'tube' can be unrolled for storage.

cosam.org - Homemade Dew Shield

Dew Shield for a Celestron C8 - Astronomy Forums

2 X FOIL BACKED THERMAL FOAM ROLL MATS CAMPING SURVIVAL on eBay (end time 03-Feb-10 19:26:00 GMT)

[SkyExplorer]

Thanks for the advice guys.

I live just inside the M25 in Surrey, so not sure what the LP is where I live, i guess its fairly bad.

So with 200mm reflector I should be able to see fainter objects that with 120mm refractor ?

What would you guys recommend I get with the scope? So far I'm going to buy a red tourch, but not sure if I need anything else.

Thanks

Steve

[pvaz]

A neutral density filter for the moon and a nice sky atlas.

Then try out the gear till you find out what you like/need.

[Astro_Baby]

Buy or make a dewshield. I bought one but people tell me you can make one with a camping mat. Best accessory I ever bought cos it keeps the secondary mirror clear of dew.

I just oustide the M25 at Redhill but I dont observe from here as the light pollution is terrible. I normaly drive off somewhere dark.