Saturn: an oblong blob through 8" newt with 10mm Ploessl - Page 2

silv (Annette) · #21 04-07-2012, 07:17 PM

make: Eden Optics. f/5. (1m length from prime to focuser) 10mm Meade ploessl.

checked it tonight:
after fine focusing with the 10mm, I could make out the bright Saturn as a bit bigger needle pin and a tiny bright plane around it - just ever so little in distant to the planet. it was more a "knowing" that there is a ring than actually seeing it.
so, an oblong tiny blob with a shadow of a doubt...

during focusing in with the 10mm, I noticed that Saturn showed the concentric circles like the manual says it should when properly colimated one particular mirror. (don't remember which mirror, now.)
that was spot on textbook.

btw: the focuser itself was ruled "trash" by the previous owner who had gotten himself a crayford (?) and was happy with it. (he kept the crayford)

unfortunately, since I joined them, the astronomy club here had to cancel all star parties (my joining was not the reason

).
I have not seen through any telescope before and don't know what to expect.

silv (Annette) · #22 04-07-2012, 07:22 PM

Quote:

Are you within the range of focus adjustment or hitting one end or the other?

I don't understand the question, Eric.
The 2 wheels on the focuser have a lot of play and it is a more intuitive than a mechanical focusing , I would say.
But from taking camera pictures, I aim for "needle pin" stars and with Saturn being closer, I played around trying to see more.
so.
hm.
what?

Edit: oh, you mean whether the focuser wheels can't be turned any further?
That I don't remember. sorry!

silv (Annette) · #23 04-07-2012, 07:24 PM

since I solved my tracking problem, we can be sure I am talking about Saturn, here, not the IIS or a satelite

(the GoTo slewed right into Saturn.)

Robh (Rob) · #24 05-07-2012, 09:01 PM

Silv,

I'm not sure that your perception of pinpoint stars can be relied on.

As Erick and Niko have mentioned, you need to check whether it is a focuser issue.

Put in the 10mm, align to Saturn and then wind out the focuser to try and focus Saturn. If the focuser is out as far as it can go, unlock the 10mm eyepiece and then try sliding the 10mm out of the focuser to see if you can get proper focus.

It may be your focuser doesn't have enough extension. If this works, you need an extender tube.

Regards, Rob

erick (Eric) · #25 05-07-2012, 10:45 PM

Quote:

Originally Posted by silv

make: Eden Optics. f/5. (1m length from prime to focuser) 10mm Meade ploessl.

I was asking because some makes of scope need a particular fitting in the focusser to allow focus to be reached.

But now you give the focal length, I suspect that you might have a tube unit designed for imaging (astrophotography). Without going into detail as to the reason, I suspect that you are not reaching focus in an eyepiece even though the focusser is wound all the way out. Is this what is happening? As Rob says, you can experiment by lifting the eyepiece higher in the fittings. With care, (and looking at the Moon is most convenient) you can lift the eyepiece completely out of the focusser and, while looking through it at the Moon's image, carefully lift it further away from the focusser while keeping it lined up on the focusser axis, and see what the observed image looks like. You can see if you get to a better focus position, then go through that to unfocussed again as you move out.

But, no worries, this is easily fixed. It needs a 2" extension tube (maybe a 35mm long one) fitted between the focusser and the eyepiece (or eyepiece plus 2" to 1.25" reducer.

silv (Annette) · #26 06-07-2012, 06:54 AM

Rob and Eric, I understand and will do what you explained.

From the little I understood so far about eye pieces, 2" are more common among the more senior star gazers here at IIS.
That - and the possibility that I might enjoy visual observing, too, has put a Crayford focuser on the shopping list - which in turn would also determine the T-adaptor or T-ring for the camera, I guess.
So if it turns out to be this focuser issue as you have diagnosed, I would solve it by "buying stuff". *sobs*

Thanks!

silv (Annette) · #27 06-07-2012, 06:58 AM

GSO Crayford - is that good enough?

erick (Eric) · #28 06-07-2012, 07:47 AM

silv, you will need to be clear about focus before you change the focusser. You are mentioning taking photographs. (I gather you have the reflector on an EQ mount.) The focusser you would choose for photography may well be different to the focusser you choose for visual observing. On a tube designed for visual use, you would fit a "low profile" focusser (GSO make one). On a tube designed for astrophotography, you would use a full height focuser - the one you have shown. So you'll need to be clear about the nature of your tube unit.

The GSO dual speed crayford is a good workhorse focusser, in both full height and low profile configurations.

silv (Annette) · #29 06-07-2012, 08:27 AM

okay. I'll find out about the focuser issue, tonight.

It was luck that I had ended up with a used EQ5 fitted with GotoStar and 8" Newt f/5 in one go at half the price of a new HEQ5.
Originally, I had only done my research around mounts (and piggyback imaging) and was going to purchase an HEQ5 without tube.

Having the tube already puts me into a vacuum of knowledge, again.

But I am not really using it a.t.m. - just preparing for the day when I will have done enough wide field imaging and want to take the next step.

I promise, before I'll spend money I will also understand what I am spending it on.
as in : will do my homework around eye pieces, focusers, filters etc.

Thank yo for reminding me of my lack of knowledge

silv (Annette) · #30 06-07-2012, 08:32 AM

Quote:

On a tube designed for astrophotography

the f/5 is good for astrophotography.
But whether the tube was "designed" for AP - which criteria would tell me that?

cometcatcher (Kevin) · #31 06-07-2012, 09:39 AM

I'd bet anything your secondary mirror is out of whack, going by that bizarre double ring holder.

erick (Eric) · #32 06-07-2012, 01:30 PM

Quote:

Originally Posted by silv

the f/5 is good for astrophotography.
But whether the tube was "designed" for AP - which criteria would tell me that?

OK, to explain a little further. And the astrophotographers can correct any mistakes I make.

When you fit a camera into a focusser, the image has to be formed some distance above the focusser to be correctly on the film (in the good old days) on at the sensor (CCD). When you put an eyepiece in, the image needs to be formed much lower, inside the focusser body. So the first difference is to have the tube and focusser mechanically designed to place the image where it is needed. Using a visual designed scope for photography is difficult - it usually needs mechanical adjustments to get the camera closer to the primary mirror. There are various ways: get the primary mirror higher in the tube on long mounting screws; saw some of the length off the tube and rebuild it; change the focusser to a lower profile focusser.. Using an imaging tube for visual is fairly easy - insert an extension tube in the focusser to lift the eyepiece above the focusser to where the image is being formed.

There might be some other differences in the size of the secondary mirror, but the above mechanical length is the main difference.

The typical visual 8" scope is an f6. An 8" f5 or f4 scope always suggests it might be designed as an imaging scope. Not always the case, but worth checking.

So you really have to see where that image is being formed with respect to your focusser so you can then decide how to proceed.

Cheers
Eric

silv (Annette) · #33 07-07-2012, 06:38 AM

thank you erick!
I think I understood that.

focused in on Saturn again.
There is enough room to wiggle left in the focusser when the 10mm is as sharp as it gets.
so (that part of ) the focusser can't be the cause.

the ring itself was clearer - as in: there was a visible tiny distance between the tiny bright blob and the tiny bright plane.
it was before moon rise in dark sky.
and: it hadn't rained for the previous 48 hours.

maybe, the speed of the scope is not meant for planets.
maybe, it's worth a try to focus in on ETA Catarina and see what there is to see - if anything. but I am not holding my breath, there.

alocky (Andrew lockwood) · #34 07-07-2012, 02:52 PM

If you put the 40mm eyepiece in, does the image appear 4 times smaller? A 10mm in your scope should give 100x, a far cry from what the scope is capable of; but certainly enough to show you rings, possibly Cassini's division. Saturn is about 20 arc seconds in diameter, so at 100x with your eyepiece (probably a 50 deg afov meaning it should cover about 30 arc minutes) there will be enough room to put 90 saturns across the field of view. You will probably want to increase the magnification to get the view you're expecting - shorter focal length eyepiece or barlow lens. No way around it, unfortunately.
If you're planning on taking up astrophotography, I seriously recommend you spend a year or two finding your feet as a visual observer first.
cheers,
Andrew

silv (Annette) · #35 07-07-2012, 03:56 PM

oohhh,
no, Saturn in the 10mm is not 4 times bigger than the 40mm.
or maybe it is... difficult to say when we are still talking needle pins. ..
it is a bigger needle pin - one you would use to sow leather with as opposed to one for sowing on buttons. hmm.

I don't want to do visual observation with the tube, now.

I enjoy the discoveries my camera does for me.
I'm not doing AP for the art.
I do it for the effect that the extended light gathering has.

So buying Barlow or eye piece is not on my short list.

Blue Skies (Jacquie) · #36 07-07-2012, 07:09 PM

From reading all that, sounds like you're targeting a star, not Saturn. Stars don't change in size when you increase the magnification, but Saturn will.

silv (Annette) · #37 08-07-2012, 02:52 AM

I know, it sounds like that.

but it is really Saturn. Goto and the ring are proof.

Thanks everyone for your input, explanations and help

Am going to learn collimation - and apart from that, wait for a star party to compare the findings with other people's gear.

I don't need to fix this immediately. I'm still very happy with piggyback pictures and learning the ropes of proper tracking.

Thanks again. Great community here on ISS

stephenb (Stephen) · #38 08-07-2012, 08:40 AM

Silv, I'm sorry you're having so much trouble with this and it is extremely commendable you are persisting with this. Most newcomers would have packed it in by now

I'd like to make a couple of points however:

Quote:

Originally Posted by MattT

Invest in a laser...I did made it all so quick and simple... GSO very good very simple to use very cheap ( sort of).
Matt

Quote:

Originally Posted by silv

nah, Matt, I'd rather not spend money on something I will only use once in a while and for something I can do without buying stuff.
Luckily, I have the time to practice everything...

Seriously consider what Matt has suggested. Invest in a good laser collination tool. If your going to own newts the they are a wise investment. Please don't consider them as simply another gadget.

Having said that, you mention 'pinpoint' when observing stars? Then i would suggest that collimation is adequate and focussing can be achieved. Im sill suspicious that either you're still not actually looking at Saturn.

You've mentioned you have GOTO facility. Have you actually looked at some other bright and easily locatable objects? I'm not taking faint galaxies or nebula. I'm talking bright, easily defined clusters! Please look at NGC4755 - The Jewel Box Cluster in Crux and NGC5139 - Omega Centauri. Have you been on a tour with the GOTO? Are you finding other beaut objects? If not, do it and see what the results are using youre 40mm eyepiece and forget Saturn for a while. If you are locating these bright objects and (with the two suggestions provided) seeing nice pinpoint stars then focus and collimation are definately not your problem and either (a) the GOTO is sending you to the wrong object, or (b) you're expectation of Saturn is too high.

You also mentioned you bought this scope from another amateur. Have you approached them for an explanation? Are they close by? If they are decent enough they will offer some assistance also.

Finally don't be discouraged but if you want to go down the long and expensive learning curve that is imaging you will need to get a grasp of visual observing.

In the end I think you need to get yourself to a local astro group when you can.

Stephen

Varangian (John) · #39 08-07-2012, 09:48 AM

Quote:

Originally Posted by silv

I know, it sounds like that.

but it is really Saturn. Goto and the ring are proof.

Thanks everyone for your input, explanations and help

Am going to learn collimation - and apart from that, wait for a star party to compare the findings with other people's gear.

I don't need to fix this immediately. I'm still very happy with piggyback pictures and learning the ropes of proper tracking.

Thanks again. Great community here on ISS

Great to hear silv sounds like the right approach. All the best

Auspom (Scott) · #40 08-07-2012, 03:22 PM

hi silv, hope you're getting somewhere with your woes. i have an 8" f5 newt and with a 10mm skywatcher ep (which is concidered to be a bit poor) in extremely light polluted skies (uk) i can still see saturns rings and 3 or 4 moons. Obviously a 5mm or 10mm with barlow will allow you to see more, but as you've stated you are more interested in imaging the 5mm would not be an advantage although a 2x or 3x barlow can be useful for imaging.as for the collimation tool, i really don't look at it as an option but a necesity. i personally prefer a cheshire collimating tool (no batteries and less chance of error) however the laser/cheshire debate has been raging since noah was a boy and will probably continue to do so. http://www.astro-baby.com/collimatio...on%20guide.htm.
this link was great for me the first time i collimated a newt.
I hope this helps and good luck with your problems. it would probably be helpful if you could borrow a 10mm ep that is known to work rather using an unknown ep. if the eps no good no amount of collimation will help.
Scott