Bino vs tele

[Hemi]

Dear members, I have an inexpensive pair of Bushnell 10x50s and a rather more expensive c925 evolution.
Sagittarius is just beautiful at the moment, almost overhead in the late evening. I can snaffle with ease (and awe) m22, m8 and m20 with the bins, but very little with the telescope: tried a variety of Mags with and without a reducer.....m22 and m20 are nigh on impossible to see in the telescope.

.....why is this? I live in Darwin....Equatorial, currently dry season, so little humidity and relatively dark skies (the Milky Way is apparent within a minute of stepping outside)....what's wrong with my scope? Or is it me

Cheers and looking forward to some insight.

[Tropo-Bob (Bob)]

I can only suggest that U start with some brighter objects like the Moon and Planets and work your way towards the fainter ones, as U become more familiar in using the telescope.

Keep in mind that it is easier to use your lowest power eyepiece when U are trying to locate objects, then after finding, U can increase the magnification.

If possible, visit a local Astronomy Club and people there will normally be very obliging in rendering assistance.

[Hemi]

Thanks Bob,

I've had the scope for 9months or so, so I'm still definately a beginner. But I'm very used to the scope, and have been observing/practicing regularly. I observe the planets every night I'm out with the scope....the last 3 months have been spectacular in this regard with Mars and Saturn passing by so close.

Some DSOs, even the supposedly easier ones like triffid, lagoon and crab continue to fox me. I've setup sky safari with my setup and so I get an eyepiece mock up to show what should be in the fov.....but alas no!

M22 is the most puzzling as I get nothing down the EP. Yet it's a perfectly obvious globular cluster even in the 10x50s.

Galaxies are another oddity.......I can pick out the sombrero comfortably but haven't nabbed any other.

Don't get me wrong, I'm loving every minute of this hobby. I'm just a bit puzzled as to how to advance. I've just bought a lumicon uhc to see if it helps.
Alas there are no astronomy clubs in Darwin.

[SkyWatch (Dean)]

I wonder if you have tried (as Bob suggests) your lowest power eyepiece with these DSO's.

For example, M8 is a big object, and quite bright: your C925 should eat it, but it is over a degree in size (around 90x40 arc minutes), so you really need to use low power to start with. The stock Celestron 40mm eyepiece (e.g.: the one that came with my C800) has only a 43 degree apov. With the C925 this will give you 58x, and around 41' true FOV: which is only about 1/2 the full size of M8. This means you will need to pan around to see the whole object in your scope: so you might have been looking at a part of it, and not realised!

M20 is about 28 arc minutes, so a fair % of your true FOV at low power, and M22 is around 32 arc minutes... so really need to use at least the 40mm plossl for these objects to start with as well.

With a low power eyepiece you should be able to see the lanes in M20 (although don't expect any colour!), and resolve stars in M22 quite happily, so I am wondering whether your collimation is out or whether your finder is properly lined up with the scope? Check your finder in the day-time with (say) the top of a distance pole.

Good luck!

Dean

[Hemi]

Thanks Dean for your help,

I've tried the 40mm with the 0.67 reducer. But haven't yet got the equipment to get a bigger tfov then that. I have my eye on a 2inch visual back and diagonal and ep's etc but haven't pulled the trigger yet, but will as the lumicon uhc I purchased on the trades here, is 2in.

The Rdf is reasonably aligned with the scope, as once all setup the smaller targets (planets) slew into EPs with relatively high magnification. Although not perfectly centered most of the time. I will try to get the ref better aligned again.

As to recollimating the sct, I've not done so ever, since purchase. I don't really know how to yet. I've checked the collimation with the defocus method and I seem to get a nice concentric pattern. I will take the plunge however and learn to check and perform collimation properly to see if that's what's causing the fuss.

I'm pretty amazed at the views I'm getting with the bins though....I've not been a mad purchaser of things Astro since starting (resistance is futile I know), but these problems have me eyeing a pair of luxury image stabilized bins or a massive light bucket like a 16in dob!

[SkyWatch (Dean)]

Hi again!

If you have tried the 40mm with the reducer that is as big as you will get with your scope: about 40 arc-minutes. The true FOV is limited by the filed-stop diameter of the eyepiece. You will get a bigger field with a 2" visual back, but you might get some vignetting with the wider field eyepieces.

If you are getting concentric rings with de-focussed images then your collimation should be OK. I wouldn't fiddle with that unless you know exactly what you are doing.

I can't understand why M22 isn't jumping out at you unless it simply isn't in your FOV: it looks terrific in my CPC800, which is smaller than yours. Have you tried Omega Centauri or 47 Tuc for comparison?

All the best,

Dean

PS: Just had a thought- the objects you are talking about are all pretty high up in the evening this time of year, and it doesn't take much of an error in the go-to drive for it to make a big difference when looking overhead. Make sure your initial set-up is spot on (do the 3-star alignment if possible), and then go-to a nearby bright star, like Antares, and re-set the go-to alignment. That might help ensure the objects are in the fov.

[Hemi]

Thanks Dean.

Tuc 47 and Omega centauri are both brilliant. Haven't seen Tuc in a little while as it gets low pretty early in Darwin.....i agree, it must be alignment. I will try what you suggest tonight. Is a reticle EP worth the purchase for alignment?

Cheers

[SkyWatch (Dean)]

Sounds promising: if you can see 47 Tuc, then you will be able to see M22! (Although not as bright of course.)

You don't need a reticle eyepiece, just centre the alignment star/s in a high power eyepiece.

Good luck!

- Dean

[astroron (Ron)]

Hi Hemi
I cannot add much to what Dean has said,very much agree that your alignment must be out,as M22 is quite big and bright in my 8"SCT and so is M8 and M20.
May I suggest you put out a call on general chat to see if there are any other astronomers in Darwin to get together,and help you out.
There is so much stuff in the milky way galaxy that is visible now that scopes over 8" could as Dean said your scope could eat.
Objects over head are notorious for not being found by scopes not being aligned properly.
Best of luck.
Cheers

[Hemi]

Thanks Ron,

There aren't many of us in Darwin, but there are a few....we've made contact on this site, but just haven't managed to get together yet. Thanks for the advice, I'm going to realign tonight.

Cheers

[Hemi]

Thanks again Members, you are correct as always, it was my alignment.
I started from scratch....realigned scope to Rdf, painstakingly to an 8mm EP on my c925 during daylight. Then 3 star alignment was carefully done using my Baader Hyperion zoom, again down to 8mm. (The seeing would not allow the ES4.7 82). The tight alignment seems to have done the trick. Triffid and lagoon were beautiful and worth the wait. The ring nebula got delivered bang in the centre of the EPs. As was the dumb bell.

I might purchase a reticled EP to take the ambiguity of visual centering of the object out of it.

Thanks again, had the most wonderful night of observing......it was 2am before I even noticed the time!

[SkyWatch (Dean)]

Sounds great! I am really pleased that you have sorted it out.

Enjoy!!!

- Dean