Small aperture and faint stars

[goranmagdic]

While I do some research into buying my first telescope (Possibly a Skywatcher 130p) a friend gave me an old National Geographic NG76AZ scope he had lying around in his attic with a 20mm EP. I aligned the finderscope during the day and when focused, got some crisp views of a tree about 100m away. I do appreciate that this isn't a serious scope, but thought it was worth a try while I make my mind up.

When it got to night, I tried aiming at the double cluster in Perseus (Which I could see reasonably clearly in my 10x50 binoculars) but could see nothing but darkness, with few stars visible even through the 6x finderscope. I managed to line it up and focus on Vega ok, the brightest star I can see from my garden.

Do you think the problem is just the small aperture? It says 76mm, but the open hole is considerably smaller than this. Thanks!

[ronin]

Suspect you will need more the 100 mtr for aligning the finder scope.

Try something about 2 to 5 miles.

76mm should be enough, there are many smaller scopes in use out there quite successfully.

Somewhat unsure what you mean by:

but the open hole is considerably smaller than this.

The top end of the tube has to be at least 76mm across, likely close to 80mm or a bit more.

Guessing it is the 700mm variant, with a 20mm EP that gives 35x and therefore about 1 to 1.5 degree field of view. The double cluster is given as about 1 degree so would just fit in. Be aware that actually aiming a scope accurately is not easy, 1 degree may seem a fair bit, it isn't.

Really I suggest something else, the double cluster can be found but does not really stand out.

Was Vega fairly sharp?

I suspect that you simply were not aimed at the double cluster, and being not the brightest it didn't stand out.

[Kropster]

Yes, sounds like the small aperture of the restriction is the problem.

This is often done to compensate for a poor quality lens.. it reduces aberrations.... but also reduces the amount of light collected and reducing the number of stars visible.

A scope like the 130P will make a massive difference... you won't believe your eyes!

[goranmagdic]

Vega was pretty sharp. I'll need to check the when I get home from work, but it seemed like some sort of plastic cap over the end with a central hole a bit smaller than the tube's diameter, so hopefully not some sort of strange 2-part dust cap!

My aiming probably wasn't up to scratch with it being my first attempt at navigating with an upside-down view, but I have a feeling the scope's quality didn't help. Vega and the stars of Cassiopeia were brighter in my binoculars.

David

[Moonshane]

it sounds like you did not remove the end cap but did remove the central small cap over the small hole used to reduce the aperture for very bright objects like the moon. I'd never use that and always remove the whole cap. you'll be able to see lots of stars in the double cluster with a 76mm scope.

[goranmagdic]

Moonshane, I think you've saved the day! My friend gave me the scope with just the one EP and the end cap on (with the small cap removed) as he had lost all of the other accessories. Let's hope it isn't so long to wait for another clear night!

Thanks,

David

[Moonshane]

you were probably looking through maybe 25mm of aperture so it's not surprising you were not seeing as much as with the 10x50s. hope you enjoy your increased aperture

[goranmagdic]

Probably the first of many rookie mistakes!

[Moonshane]

we've all been there!

[ronin]

It did pass my mind, but I half assumed that the 76mm wouldn't have a small hole in the main front cover, just didn't seem much point in it.

When you get the chance aim it at Jupiter, even at 35x to 40x if the image is reasonable you should see banding. If you miss it now it will be another year.

[goranmagdic]

Being a pretty cheap scope, it's probably just another thing they can list as a "feature" like the crazy 500x magnification!

[Astro Imp]

Probably the first of many rookie mistakes!

You can't call yourself an amateur astronomy until you've made a few of the basic mistakes. The classic is leaving the end cap on the scope but it doesn't seem as though you'll be able do this. I guarantee that when you get your better scope you will do this at least once and don't forget you can't focus with the locking thumbscrew tightened. You can see I'm talking from experience 

[Moonshane]

I once went to check out a possible observing site with only two of my three pier legs.

[Kropster]

Everyone leaves the end cap on at some point.

It is a sort of initiation rite.

[AlexB67]

Everyone leaves the end cap on at some point.

It is a sort of initiation rite.

Been there, done that, guilty as charged

[goranmagdic]

After weeks of reading reviews and research, I've decided to bite the bullet and order a SkyWatcher Skyliner 150p. Let's hope I remember the cap on this one!

[acey]

Persevere with your little scope - it's more aperture than Messier used to make a lot of his discoveries. Just try and get it to a truly dark site, where you can see the Milky Way naked eye. Then you'll also be able to see the Double Cluster very easily with the naked eye, and it will be lovely in the little scope. A 76mm scope has about the same light grasp as 50mm binoculars, so for DSOs you may find the bins good enough, but the scope allows for higher magnification which would be useful on planets. The rings of Saturn, red spot on Jupiter and polar caps of Mars were all discovered with apertures no greater than yours, and probably poorer optics - though used with highly experienced and patient eyes. Good luck with your 150P, which will give you even better views, and don't let other people infect you too quickly with their own aperture fever.

Just be aware, if you're in Scotland, that as the nights get shorter it becomes impossible to get full sky darkness, so it may not be worth making a dark sky trip until a moonless night in late summer or early autumn. Plenty of time to figure out where to go. Fife has some pretty dark corners from what I recall. But not if the moon is up.

[goranmagdic]

Thanks for the tips. Hopefully I'll have room to keep them both. It'll be interesting comparing the views they both give.

[goranmagdic]

I didn't give up on the little scope. Last night, it was pretty cloudy but I managed to get 10 minutes of clear sky to aim at Jupiter and see the 4 moons. Amazing the difference I can see with the cap off!

[Astro Imp]

I didn't give up on the little scope. Last night, it was pretty cloudy but I managed to get 10 minutes of clear sky to aim at Jupiter and see the 4 moons. Amazing the difference I can see with the cap off!

Good to hear you're making progress and you seem to have a sense of humour, it certainly helps in this frustrating hobby.

Good luck.

[Myopicus]

IMHO . . .  there's a lot of 'kit lust' associated with many hobbies (astro, woodwork, motors, fishing, blah blah).  Ultimately it's base level coveting;  'I would be able to do x if only I had y so I won't bother until I have the next bit of kit' . . . and the next and the next. Really good to hear an account of somebody getting the bug with an acquired scope . . . and just getting on with it the best they can.  Yay!

The 150 will serve you well, a brilliant upgrade.  CLEAR SKIES!

[nephilim]

I once went to check out a possible observing site with only two of my three pier legs.

Travelling miles to a dark sky site to find i'd forgotten my EP's, travelling miles to dark sky site to find i'd forgotten counterweights, travelling miles to a dark sky site to find i'd forgotten counterweight bar.............................Havn't forgotten the scope yet but i'm sure thats just around the corner 

Steve

[Myopicus]

Travelling miles to a dark sky site to find i'd forgotten my EP's, travelling miles to dark sky site to find i'd forgotten counterweights, travelling miles to a dark sky site to find i'd forgotten counterweight bar.............................Havn't forgotten the scope yet but i'm sure thats just around the corner 

Steve

LOL! Done that doing a pole-lathe demo at a medieval charter fayre show - forgot my treadle (much like forgetting your entire tripod). Had to do a 30 mile round trip to retrieve, dressed all the while in woollen tights, smock shirt and strange hat.                Yes, the police stopped me.      wasn't good       a  LOT of explaining.     

edit:  and i was hungover.    

[ronin]

Tonight:

Scope in car, tripod in car, eyepieces in car, power supply in car, extension lead in car, spare batteries in car.

No damn handset in car.

At least I had the chance for other things to occupy the evening.

Now I need to find that handset.

A goto without a handset is of limited use. Very limited use.

[Rustysplit]

I have left my aperture mask on the dob and then wondered why the views were so dim compared to what I was used too