Trouble with focusing and Barlow

[Special K]

Hi, I find it quite difficult to focus my 130P on Jupiter at 108x using my Barlow. I am wondering if it is inexperience or if the supplied focussing assembly is not ideal. I am getting a higher mag EP and worried i will have more of the same issues. There are some plastic components in the apparatus and wonder if I should upgrade (though funnily enough I can't see anything that would fit a 5" newt on FLO!). I need something that can make more subtle adjustments. Or am I just being a Rookie?!!!

[crashtestdummy]

With the standard focuser on my 300p i couldnt find good focus on my 6.7 and 8.8mm eyepieces.purchased a duel speed focuser and the fine focus knob makes the world of difference.

[Moonshane]

couple of queries. are you letting the scope cool down before viewing? I usually allow 10 minutes per inch of aperture for full cooldown but you can observe at low power (maybe 50x) almost straight away. higher power needs longer cooldown.

are you observing when Jupiter is low? this will have the effect of fuzzy images as you are looking through more atmosphere

the quality of your barlow may not be that good but if you allow cooldown and the objects to get higher in the sky I'd expect you to be reaching perhaps 130x comfortably.

[Special K]

Hi Moonshane, I'm getting it good and cold (1 to 2 hours) and am having a go at Jupiter at its highest. But it's hard to tell if it is due to average seeing. I got a real clear focus about a month ago so know its possible. I think maybe I should keep at it but would be better to have a fine tuner to work with. Thanks for asking.

[Moonshane]

sorry, I actually missed the barlow you have and see it's a good one. if you are cooled and the target is high (and presuming you are using your 12mm BST barlowed) I am surprised you cannot get a sharp image. perhaps it's collimation?

[Moonshane]

I should add that I got very sharp images with a helical focuser (if this is what yours has) and did not have any issues getting focus on my old 6" newt at around 130x.

[Special K]

sorry, I actually missed the barlow you have and see it's a good one. if you are cooled and the target is high (and presuming you are using your 12mm BST barlowed) I am surprised you cannot get a sharp image. perhaps it's collimation?

Good idea: I'd better check this out again. Helical focuser might be an option, thanks.

[Special K]

UPDATE! Tonight I checked collimation and that still looks correct to me. I checked the screws around the focuser and tightened those up as they had a little give in them. I also slightly tightened the two screws for the pinion mount and that effectively put a little more resistance on the pinion twist. The weight of the Barlow and BST together puts a little sag on the plastic tube of the focus assembly and I wondered if that had any negative effects on focus.

Cooled the scope tonight (and wasn't it a grand one if not for a 100% full moon?!) for a good 90 minutes before attempting anything. Messed around showing my son some clusters etc for another hour and then trained it on Jupiter for the real test. If it were not for the moon being right on top of it, I think I would have had some exquisite views. But I really didn't know what else I could run the test against so went for Jupiter regardless. Suffice to say I have never seen so much detail as I have tonight!!! I believe I could make out the GRS and that is a first. I found the greater resistance on the focus knob helped a wee little bit but it is mainly perseverance that paid off. I observed for at least 20 mins with varying EP's and have concluded that the scope and EP's are ok, the focuser isn't ideal but with effort it can work, but that the atmospheric conditions have been the most important factor in image quality.

My obs tonight showed fleeting periods when the image was remarkably clear (and one moment when I was totally floored by the level of detail on those belts ) and some intervals when it became fuzzy. I think my obs to date have been too brief and I just need to persevere more. I think the seeing tonight in SE England was average and that the moon was playing havoc! I look forward to the next chance and also the pending delivery of my 5mm BST! Sticking that on the end of the Barlow will be the ultimate test at 260x!!! I'm also curious how the 5mm eill focus on its own. Clear skies......and plenty of patience!

[Moonshane]

sounds like you are beginning to learn the art of planetary observing your description is exactly what I'd expect - well done for a bit of investigation and tweaking with the rewards that usually comes from it.

[Special K]

Another UPDATE!  (who knows, someone might find this useful!)

I received my 5mm BST yesterday and plugged that in for Jupiter last night.  There happened to be a shadow transit from Europa at the time and this appeared as a needle point black dot on the planet.  Now if that isn’t focussed I don’t know what is!  What I noted, for whatever atmospheric reasons, etc, the belts were somewhat fuzzy as I normally struggle with.  I’m thinking my issue is more due to contrast rather than focus and am addressing this issue already in considering some filters (weighing up Neodymium vs Color filters) for planetary observations.  Thanks a lot for the encouragement, Moonshane!

The 5mm on its own was about the same effort to focus as the 12mm with 2x Barlow.  When I slapped the 2x Barlow on the end of the 5mm I get a nice big disk but just couldn’t get the clarity.  However, I wasn’t surprised by that as I don’t think conditions were optimal and I was effectively maxing out my scope’s magnification potential at 260x.  I might have even had a little condensation or frost on the secondary.   This time the scope was so cold, it was literally frozen!  Now that’s something I’ll miss in the summer time, a nice cold one!!!

[tingting44]

hi special mate, i have the same SW 130p as you and im in the same boat as you mate, i totally hate the crappy focuser, especially when you have a dslr connected, its just terrible i cant put up with this focuser any longer, would this fit our SW 130p? as it has to be better then the Rubbish it comes with

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p2625_Lacerta-Mikrountersetzung-z-B--fuer-Skywatcher-Crayford-Auszuege.html

[Moonshane]

unfortunately I think you have a helical focuser (i.e. one that focuses like a camera lens?). the dual speed adapter shown is for crayfords. maybe a pic of your focuser would help?

[Special K]

Hmmmm. The principle looks fine to me and I would be tempted to have a go at replacing it. However I'm not sure it is compatible with our model. Maybe a well placed email to them for advice/confirmation? It is just the kind of thing we are looking for though! Let me know if you do it!

[Special K]

unfortunately I think you have a helical focuser (i.e. one that focuses like a camera lens?). the dual speed adapter shown is for crayfords. maybe a pic of your focuser would help?

130P is rack and pinion and not helical (unless I'm a fool). It has two adjustment knobs: equal on both sides. I would welcome a fine tuning helical and shame I can't just incorporate one.

[tingting44]

unfortunately I think you have a helical focuser (i.e. one that focuses like a camera lens?). the dual speed adapter shown is for crayfords. maybe a pic of your focuser would help?

hey moonshine thank you for helping here is the pics i took just a second ago....its a terrible setup

IMG_4040 by tingting44, on Flickr

IMG_4041 by tingting44, on Flickr

Hmmmm. The principle looks fine to me and I would be tempted to have a go at replacing it. However I'm not sure it is compatible with our model. Maybe a well placed email to them for advice/confirmation? It is just the kind of thing we are looking for though! Let me know if you do it!

yes i will email them my friend and let you know what they say, if anything it will be an xmas prezzy for me so wont be till near the end of december till i do get it if it does fit

[tingting44]

email sent, so hopefully we will know if it is compatible soon'ish

ps...sorry for intruding in your thread by the way mate

[Moonshane]

ah, sorry. not seen that one before. many people use 'automatic' focusers on these types and to good effect. might be worth trying a used one if the focusing 'knobs' are removable? http://www.firstlightoptics.com/astronomy-cables-leads-accessories/skywatcher-auto-focuser.html many people make their own too but I am rubbish at electronics.

I think I am thinking of the heritage truss tube one that has a helical focuser http://www.firstlightoptics.com/dobsonians/skywatcher-heritage-130p-flextube.html

[tingting44]

with the ammount of scopes out there its easy to get them mixed up moonshine lol

mhhh i was looking at them auto focusing unit;s a while ago but just was not sure if it would be any different from the setup now as it still has to turn the original horrible gears right? ahhh i just dont know now lol, i just took another look and no the focus knobs are not removable

[tingting44]

just watching this at the mo, might be helpful to others, just showing in detail how the auto focuser is assembled

[tingting44]

got a reply on the auto focuser, still waiting for a reply on the Lacerta 1:10 micro transmission for Skywatcher

any hoo here is the nice reply from FLO

Martin, Nov 30 07:23 pm (GMT):

Hi

The focuser is listed as per the suppliers spec, the review is a customer review which does suggest that this unit will work with the 130 , we have not tried it with a 130 so can only advise as per suppliers spec..

This auto focuser is used on a range of different telescopes, many have modded them to get them to work

You are welcome to buy and try but we can't guarantee it will work, treat it gently till you know if it is ok and you can return it if it doesn't work

Regards

Martin

M Young, Nov 30 05:25 pm (GMT):

hi i am looking at this for my SW 130p as i just cant stand the horrible

focuser any more now im a bit confused as you state it does not fit the

130p and there is a review saying it does fit? would like to hear from you

guys personally rather then a review before i buy it

[Special K]

Yours looks a lot different than mine! No intrusion, happy to get feedback!

[Moonshane]

it's broadly the same though so the same applies

[tingting44]

morning

Yours looks a lot different than mine! No intrusion, happy to get feedback!

i see what you mean mate!! the details are very different in both scopes considering they are suppose to be the same scope? i bought mine from FLO, where did you get yours from? i think i bought it probably within 1 year ago?

ps. how do you get your pic nice and small like that, so when you click it, it goes into a link for a bigger image?

...here is another pic of mine in roughly the same orientation as yours, quite different....

IMG_4044 by tingting44, on Flickr

[brucen]

morning

i see what you mean mate!! the details are very different in both scopes considering they are suppose to be the same scope? i bought mine from FLO, where did you get yours from? i think i bought it probably within 1 year ago?

ps. how do you get your pic nice and small like that, so when you click it, it goes into a link for a bigger image?

...here is another pic of mine in roughly the same orientation as yours, quite different....

IMG_4044 by tingting44, on Flickr

I have this focusser on mine and the knobs do come off although it does take a lot to unscrew them the first time. I took mine apart and held it in a vice as the bar was bent and I needed to straighten it. I also read a thread on here some time ago that the auto focuser fits this one without modification. Father Christmas is bringing me one so I can't say for certain as yet though. I want one as it should make using the webcam a lot easier.

[tingting44]

hi bruce, ah thats good to know that the knobs do come off then, i did try last night but couldnt even get the to budge lol i didnt want to try too hard and break something tho lol but knowing that they do unscrew is good and will have to have another go at it, i think im leaning towards this auto focuser now tbh......mhhh lol,