Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Choosing a telescope.

AstronomicalCheeki

Recommended Posts

AstronomicalCheeki

AstronomicalCheeki

Posted
Posted

Hello guys as you see i am new in the forums and im starting my stargazing adventure.I want to use my telescope as an astronomical and a terrestrial telescope so preferably a mak or a refractor.My budget is 450 dollars for both telescope and tripod.

I already found one good telescope http://skywatcher.com/product/bk-1206az3/ Its the skywatcher 120/600.

Let me know if you have any other telescopes.Thank you

Link to comment
Share on other sites
  • Replies 34
  • Created
  • Last Reply
davyludo

davyludo

Posted
Posted

Hi and welcome!

I have the smaller version of the skywatcher (ST102). The AZ3 mount really just manages it - I know some people use the AZ3 with the ST120, but I think most end up modifying the mount with counterweights. 

The ST120 would probably give you chromatic aberration (CA) and false colour if used for day time terrestrial viewing, due to it being a short achromatic refractor. Other, more experienced members may be able to advise on this.

I also have skywatcher skymax 127 mak, which I only just got recently and haven't managed to use much because of the weather. It's really good from the short time I've spent with it. However I think the field of view might be a bit narrow for terrestrial observing?

Both the Skymax and the Startravel range from skywatcher are great starter scopes - I've certainly enjoyed using them both so far. Although I only use them for stargazing, so don't have a lot of terrestrial experience. I use an AZ5 mount for  both of my telescopes.

I know you want to use it for astro and terrestrial, but which one are you mainly interested in? Also, what are you hoping to look at most (moon/planets/clusters/doubles)? 

 

Link to comment
Share on other sites
ronin

ronin

Posted
Posted

As the budget is $ then I assume the US, in which case have a look at the ES AR80/640 offering.

It is an 80mm scope with a reasonable Alz/Az mount so will cover a fair number of astro viewing, and if you bought an erect image prism you can use it for terrestrial. At f/8 CA should be present but minimal, at 640mm FL you might get to 120x for Saturn (5mm eyepiece) but it is likey at the very top of what it can do. And it may not make it. Good for moon and Jupiter. Decent fielsd of view with a 25mm or 30mm plossl eyepiece.

Also it costs $150. and as you will no doubt soon require an additional 2 or 3 eyepieces you have budget remaining for that, and at some time you can pickup a solar filter for the front and go solar viewing.

After all that I still guess you would have budget left over, not a lot but some.

Link to comment
Share on other sites
davyludo

davyludo

Posted
Posted

I think the mak would be better if your main aim is the planets (in terms of astro observing). The mak 127 might be a bit heavy for the AZ3 mount, a 102 mak would be better as its a bit lighter.

However I'm not sure a mak is the best for terrestrial. Might be worth looking at longer focal length refractors. Not something I know much about I'm afraid, but I'm sure others will have good advice.

Link to comment
Share on other sites
Ricochet

Ricochet

Posted
Posted
2 minutes ago, AstronomicalCheeki said:

Thank you again.So if i understand the shorter the refractor the more ca it has.Right?

For a given aperture, yes. See this table below for an idea on how it varies for different size achromats.

CA-ratio-chart-achro.jpg

You might get away with using an ST120 for terrestrial, but the only way that you will know if you are happy with the view is by trying it. It also depends on how you expect to use it. If you live up on a hill and have a great view across a valley from your garden it might be ok, but if you live at the bottom of the valley and are imagining carrying it up the hill to find a vantage point then it is a completely different story as it is quite a heavy scope for that.

The problem is that any scope you choose will have compromises for your intended purposes. Astronomically you will want a large aperture to support high magnification and gather lots of light but terrestrially a small and lightweight scope is more suitable. I "solved" the same problem by buying two scopes, an 8" Dobsonian for astronomy and a 65mm spotting scope for terrestrial use. However, to do this I think that you will need to increase your budget and patiently wait for suitable telescopes to appear in the second hand market.

Link to comment
Share on other sites
Ricochet

Ricochet

Posted
Posted
1 hour ago, AstronomicalCheeki said:

Thank you so much for the explanation.But i heard mak has really minimal ca so wouldnt it be better for terrestrial.

Yes and no. It would be better from the CA point of view but by design a Maksutov has a long focal length, which means that it produces high magnification, small field of view images. For example the 90mm Skywatcher Mak has a focal length of 1250mm with the widest field of view possible coming from a 24mm 68° eyepiece or a 32mm 50°. The 24mm would give 52x and 1.3° and the 32mm 39x and 1.3°.  Both of these magnifications are high enough to be affected by heat haze on a warm day and for comparison with my spotting scope my "high power" fixed eyepiece gives 1.75° and my normal power gives 2.5°. However, if you are only intending to observe stationary objects then the small field of view may not be an issue.

I have seen a couple of people post here about owning an Omegon MightyMak 60. This has a much shorter focal length (700mm) so will allow you lower magnification, wider field of views than the 90mm. However, 60mm is too small for astronomy I think so you are back to needing two scopes.

I think both Maksutov options have photo threads so that you can attach them to photo tripods for terrestrial use but you will also want a correct image 45° diagonal for terrestrial use.

Link to comment
Share on other sites
davyludo

davyludo

Posted
Posted
1 hour ago, AstronomicalCheeki said:

Also would the az3 be able to hold 127 mm mak?

I've had the mak 127 on my AZ3 for a quick test. The mak is very much at the limit of what the AZ3 can cope with. It's a bit wobbly for high magnification work and struggles as you increase altitude.

Again, for terrestrial it's probably acceptable as you won't be going too high in altitude. But I don't think it would be my option.  The 102 mak would be less strain on the AZ3.

Are you sure you're happy with around 1 degree fov? I only ask because personally for a terrestrial scope I'd be looking for more than 1 degree. My ST102 with a 25mmm eyepiece gives 3 degrees.

Link to comment
Share on other sites
Ricochet

Ricochet

Posted
Posted

The main difference is the size. The bigger the size the more light it collects and the higher you can push the magnification, but the heavier the telescope gets. The 127 is going to be the best for astronomy but the 90 will be a lot easier to carry around for terrestrial viewing.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.