star hopping help

lesbehrens (Les) · #1 22-09-2008, 03:13 PM

hi. i was wondering if i bought a red dot finder would it help me find my objects better than looking through a finder scope? i haven;t used a red dot finder befor so thats y i am asking.
are there any other suggestion that can help my until i buy my Argo.
les

erick (Eric) · #2 22-09-2008, 03:34 PM

Yes, an aligned "red dot" (a "unity") finder should get you to where you recognise the view in your 8x (say) finder so that you can get the object (or location with faint object) into a 30mm (say) eyepiece FOV. From what I have seen, it's probably worth spending Telrad-type money, rather than buying the really cheap dot versions.

NQLD_Newby · #3 22-09-2008, 03:37 PM

Hi Les,
I think it is personal preference. My first scope had a red dot finder and I found it incredibly easy to use. I recently upgraded my scope and the new one has a a finder scope. To be honest finding objects is easier in the finder scope, if you don't like star hopping. As I'm sure your aware the red dot finders don't have any magnification factor, so if you can't see it naked eye, you can't see it with the red dot finder. The way I used to use it was estimate where the object should be with regard to brighter stars in the area and point the scope to that spot. However you then have to compare what you see with a star chart to find exactly where in the area you are pointed and then star hop the rest of the way. The only other suggestion I have is a telrad or similar device which has the rings at varying degrees away from the centre which may allow you to estimate your positions a little better. Star hopping is a great skill to learn, because even with teh finder scope there is many objects that need to be star hopped to. hope this helps.

NQLD_Newby · #4 22-09-2008, 03:38 PM

You beet to to it Eric.

erick (Eric) · #5 22-09-2008, 03:53 PM

I see your beet and raise you a turnip

Les, another approach is using a laser pointer to direct the scope. (Lots of issues here around prohibited weapons, safe usage, upsetting other observers or particularly astrophotographer folks! Search the threads on this site.) However, I found that with laser aligned well, I could point the scope accurately enough relative to the stars that I could see naked eye, to have my object in a 30mm eyepiece field. You need to have a good sense of location in the sky relative to the star chart or planetarium view on your computer screen.

lesbehrens (Les) · #6 22-09-2008, 05:42 PM

hi. i see. if i do the laser option how much would the brackets be to mount it?
i do get some good results with looking through my finder to help locate my objects, its just some times i miss the object entirly. eg i can find the dumbbell neb easy some days other time i get lost.
les

hlokk · #7 22-09-2008, 06:51 PM

I made a bracket out of some PVC pipe I had laying around. I cut a hole in a film canister lid which happened to fit perfectly over my pipe (very close to the dimensions of a film cannister which may come in handy for eyepiece extensions or camera holders).

The laser pivots at the end, then I drilled two holes in the PVC at right angles at the other end and threaded some bolts in (reamed out a thread with the bolts). Then I attached rubber bands to tension it (a spring underneath like with finder scopes would be better). I used another bolt that i twist to turn the laser on (and keep it on).

The laser is sooo much easier to point around than the finder (which I have to line up the tube first which takes a bid of fiddling). 47 Tuc is easy to get as its kind of in a parellogram, so I can point the laser to roughly where it is by eye (cant see it naked eye in my light polluted yard), then I can see it really easily in the finder, then the eyepiece is no problems. I had to star hop from n tucana beforehand (I forget the star name, but its the brightest in tucana, up to the left around midnight).

Managed to find neptune last night as well which I would be able to do with the finder alone with my noobiness :p
I had to have the laser offset so I dont see it in the eyepiece though.
(thats when the laser is bright enough to be useful.... :s)

As for vaguely pointing the scope, something I recon could work ok for widely framing a star would be a toilet roll tube (ok, dont laugh :p). Just so you can pick it up in your finder. PVC would be more professional looking and dew proof though.

Bintel sell a laser bracket if you arent the DIY type https://www.bintelshop.com.au/Product.aspx?ID=8110 (its for the skyhop though, so it might take a bit of wrangling to fit the telescope).
I've heard some people pick up a small, cheap finderscope on ebay or garage sale, etc for around $10 then chuck the finder away and put the laser in it.

erick (Eric) · #8 22-09-2008, 10:03 PM

One small piece of wood - file groove on top.
One out-of-date fridge magnet - chop up and superglue suitable piece to wood.

Plonk piece of wood on OTA up against finderscope dovetail bracket, or against edge of focusser.

Calibration - take laser out of top pocket (where it is kept warm so beam doesn't fade) and place on groove. Push wood against finderscope or focusser straight-edge. Check beam clears end of scope. If not, get bigger piece of wood. Look through low power eyepiece and make small adjustments until end of beam is close to centred in eyepiece. If necessary, can shave/file the wood edge and the groove - but I find with the magnet, once I have the groove right, I just have to slide it to the right position and it holds the position for the night if I'm careful placing the laser on and removing from the wood.

That done - operate. Place laser in place, push button, move scope until the end of beam is at desired location. Laser off and back into pocket. Observe object.

Required - steel OTA

hlokk · #9 23-09-2008, 01:27 AM

Good idea erick. How do you keep the laser pointer on the block/turn it on?

lesbehrens (Les) · #10 23-09-2008, 07:08 AM

i agree. that is a good idea. ill start work today on it.
les

Quote:

Originally Posted by hlokk

Good idea erick. How do you keep the laser pointer on the block/turn it on?

drmorbius (Randall) · #11 23-09-2008, 07:18 AM

Hey Les,

While a laser pointer is another excellent approach to finding your away around the night sky, be aware that they can stuff up any imaging going on around you, so you wouldn't be very popular using one at star parties like Astrofest or Barambah.

But for working at home or, more importantly, learning to star hop from a one of the astronomy masters, they're a terrific.

cheers

drmorbius (Randall) · #12 23-09-2008, 07:20 AM

Oh, and Eric... that's a very clever solution... might get myself a laser pointer...

erick (Eric) · #13 23-09-2008, 09:18 AM

Quote:

Originally Posted by hlokk

Good idea erick. How do you keep the laser pointer on the block/turn it on?

Very manual operation - I hold it in place in the groove on the block with my right hand and just use my index finger to operate the button/switch. I hold/move the tube with my left hand (as usual, fingers curled around into the light path, thumb outside), right hand holding laser on wood, perhaps eye at eyepiece to check the end of beam is visible in the eyepiece (that I haven't knocked the wood out of place).

When sure that laser is aligned with scope (ie. end of laser beam is visible in the eyepiece (doesn't have to be well centred), then look at sky and move scope until laser is pointing to the object or location of interest. I'm forever working from charts saying to myself something like - OK, it's 3/4 of the way from that star to that star and up a bit off the joining line - then I point the laser/scope to there. Once I get there, it's laser off and popped back into top pocket to keep warm, long distance glasses tossed off so they hang from the cord I have them on, then eye to eyepiece and enjoy.

Shouldn't need photos? - it's so simple.

(got the idea from seeing someone who had removed finderscope and bracket and was balancing the laser inside the dovetail saddle, up against one side.)

(Of course, my recently commissioned Argo Navis should see the end to regular laser pointing.)

hlokk · #14 23-09-2008, 01:02 PM

I was thinking before that you attached the laser to the wood, then put the whole thing in your pocket (which would be useful for keeping it warm in your pocket and in place on the scope). Might try that later (its funny when your ideas come from misunderstanding something else, lol).

I got my binoculars yesterday, and tried them out with my laser pointer. That and a good star chart (was using the skymaps, taki and stellarium) I could kind of straddle the scope, move it with one hand and hold the binoculars with the other. The sky around my house is very light polluted, so binocs are needed to see a lot of stars. It was very easy to star hop using the the laser to point where the binocs are. Then when close by just use finder (got it in the eyepiece half the time straight off).

E.g. I cant see 47 tuc with naked eye, or small binocs, but with the 50s and the laser i got it in the eyepiece in about 10 seconds

(the parellogram I was talking about doesnt have any stars in tucana. I must of been thinking of achernar before).

Crusader · #15 28-09-2008, 10:09 PM

I'm jumping in a bit late here, but a red dot finder definitely makes life easier. I recently got a cheap Skywatcher RDF to add to my XT10. I simply stuck it on top of my existing RACI finder and it makes tracking down objects and actually knowing where your scope is pointed much easier.

I use the RDF to locate the bright stars I'll be jumping from and then use the normal finderscope to zero in on what I'm looking for. No more getting "lost" or mistaking a not so bright star for your reference star. It also makes it easier to line up the right star again if you need to redo a jump.

After some practice and a bit of memorising I managed to consistantly put the Helix Nebule in my EP FOV by simply pointing the RDF in the right place. An added bonus is that you can also "show" people what they are looking at by telling them to see where the red dot is pointing.

Of course a Telrad would be a better option if it's available. Sadly they aren't available over here and importing would have been 3 times as expensive for the shipping as the price of the Telrad, so I make do with a cheap RDF.