so many questions.. so little time.. =(

[AweSIM]

hi all..

ok.. instead of cross-contaminating threads with off-topic questions.. which decreases usefulness of the forum (cuz the thread name doesnt reflect all the answers within).. im spawning a new thread to lay out all the questions in my mind.. given how helpful this forum has been to me.. im sure ill get the answers i want.. =)..

the equipment i have is:

- skywatcher explorer 200/1000..

- 28mm 2" stock LET EP..

im trying to raise cash for an neq6 plus a couple of good EPs, barlow and camera adapter.. till then, i just cant keep my hands off my scope.. so every clear night that i get.. i take it out.. and carefully prop it up against an obstacle to hold it steady and observe thru it.. at times i even screw off the lens of my nikon D90 and hold it up against the focuser and shoot away.. stupid yea.. but dont laugh.. =P.. so.. yea the view is always jittering a bit..

1. ive had 3 attempts at collimation so far.. im my room the attempts seem great.. but when i move the scope out im somehow not satisfied with the results.. the stock EP isnt up to my expectations at all.. it shows field darkening (kidney beans?) that moves when i shift my eye around.. plus it shows red and blue hues around everything.. i think its cuz its a single-element EP (not achromatic) and stock EPs arent good in the first place.. plus objects near the edge are visibly blurred.. i think thats not the EPs fault but the fact that the scope is an F5 and needs a coma corrector.. correct me if im wrong.. (see what i did there? =P).. and if so.. can you recommend one for me? last night i shot some images of the moon and jupiter.. and no matter how much i tried.. i couldnt get a perfect focus.. i was shooting at 1/400s so a hand-shake couldnt have caused the blurring, could it? ive tried shooting bursts during which i use the fine focus control of the crayford to go from one end of focus to the other.. the images do get crisp as i go thru the focus.. but never near the qualities ive seen on this forum..

2. im looking to get some EPs.. ive seen some pretty expensive ones that i drool for but know i cant get anytime soon.. costing about EUR300+.. then there are some which cost around EUR30.. im forced to think if these are any good? im looking to buy some EPs from Tekeskop-Express.. id go for an EP around 5mm.. one around 15mm.. one around 30mm (to replace the LET stock EP).. and a barlow.. what do you guys suggest? i am interested in DSOs but you need imaging for those.. for visual observation, planets are a much better target.. so im looking for EPs that can give me good magnified views of venus thru to saturn.. what do you guys suggest? and what price bracket should they be in?

3. ive tried DSLR astrophotography too.. but what i dont know is if its possible to magnify the image.. the moon fills up half the area of the sensor easily.. but jupiter fills up about 50x50 pixels in the 4000x3000 image.. now i know i can bump up the magnification using a shorter EP and may even attempt afocal imaging.. but can the magnification be changed when imaging with a direct DSLR connection (thats prime focus imaging, right?).. can i make jupiter any larger than 50x50 in my DSLR?

4. ive been testing registax recently.. but its giving me problems.. fails to open some avis.. fails to generate align points sometimes.. fails to align images.. and usually i have to manually remove images which are too far off alignment.. and when stacking.. i almost always get ghost images due to poor alignment.. ive seen many tutorials but im looking for a tutorial which not only shows you what to do.. but also provides a set of images to test on.. this way i would be able to see exactly what am i doing wrong.. it may be wishful thinking.. but if you guys use reigstax successfully, maybe you could send me a few raw images / avi + instructions on what settings to set and the expected final image.. that would be the best.. just in case.. my email address is awesim@gmail.com..

thanks a lot ppl.. =)

awesim..

[Glen]

Hi awesim, wow lots of questions! I can't really answer as i don't have that scope, but have a look at this site while you wait for info.

Videos of the planets: Jupiter, Mars, Saturn, Venus and the Moon, waiting to be downloaded. Amateur astronomy.

lots of videos to practice and compare your results.

Best of luck

Glen

[AweSIM]

hi glen.. wow!!! just what i needed!!! thanks a million!!! =)

[umadog]

Some thoughts on your 3 points:

1. Why aren't you satisfied with your collimation when you're under the stars. What criteria are you using?

"it shows field darkening (kidney beans?) that moves when i shift my eye around" This may be normal, it depends what you mean. The eyepiece is unlikely to have a single element, by the way. Some of the cheaper Plossls have only 3 elements.

The blurring around the edge will be two things: astigmatism due to the eyepiece and coma due to the primary mirror. At F/5 you won't see too much coma above about 80x so it's only an issue at all at lower powers. Generally, there isn't too much coma at F/5 so I think most of what you're seeing is astigmatism due to the eyepiece. You want to get better eyepieces before you spend money on a coma corrector. When you look at the reviews of different eyepieces, make sure that they have been tested at <F/5 when you're looking at the comments. Hyperions, for instance, work well at slower focal ratios but are a disaster at F/5 and faster.

There's no way you'll get good results hand-holding the camera. You need to fix that first and worry about focus later. Good quality images are hard to get.

2. Expensive eyepieces generally are those with wide fields of view. These need to be well made for the view to be free of aberrations (such as astigmatism) across the field. That costs money. A good Plossl, on the other hand, has a narrower field and is easier to make well. These are therefore cheaper. I have some old Meade Series 3000 Plossls which work pretty well. Televue Plossls are also good. I Others will also work well, I'm sure. You could buy second hand and sell those which don't work out.

I can't really specify a price bracket. To bring up the earlier example, Hyperions work well at large focal ratios and aren't cheap but they won't do a good job with your F/5. Paying more doesn't necessary mean you will get better results. You need to buy the right thing.

[ronin]

A 28mm eyepiece in a 1000mm FL scope gives a bit less then 40x, are you sure it is a 2" ? that is not usual, also do you mean LER ?

Hand holding a camera is not sensible, you are moving so focus will be adjusting. Taking pictures via a scope is not the same as in daylight and you have used daylight ideas. An exposure of Jupiter may easily take 30 seconds if you hands moved in any direction by more then a pixel you get a blurred image.

Consider that you actually have a 1000mm lens on the front of your camera and need long exposures, You would have to use a solid tripod during bright daylight, throw in that the lens and camera aren't even attached to each other and what do you expect.

As you want an NEQ6 I assume that you have a Dobsonian mount. If so forget astrophotography for now. For AP you want a driven EQ mount, until then don't bother. Actually the post implies just the OTA no mount at all ?

I take it out.. and carefully prop it up against an obstacle to hold it steady

If the TS eyepieces are plossl's then at the shorter ones you will lose eye relief. I would suggest 5mm, 7mm 10mm and then something like a 15 or 20 and a 32mm. Don't get the 5mm first.

How well a plossl will work in your scope I don't know, it is often said that at f/5 you need to use better then the budget offerings. Although the GSO plossl's have a good reputation. Not sure if the planetry's are better for your scope, usually better eye relief and a little wider field of view.

Registax is really for avi's from a web cam and again I see no mention of one. It needs something half reasonable to start with. The software operates by determining good matches, if there are no good matches then it is stuffed. Again a handheld camera isn't going to supply that.

Worst case at this time is that you have 1 eyepiece at gives low magnification, no mount and are trying to get images with no attachments or traking facilities by hand holding a camera at some undefined position. Short term buy a 7 or 8mm eyepiece along with a 15 or 20mm and get observing. If the scope is just an OTA they search for plans to build a Dobsonian mount and get some ply wood.

[AweSIM]

thanks a lot umadog and ronin for those valuable words of advice.. =).. some thoughts about the points mentioned in the two posts..

1. @umadog.. collimation.. ive used astrobabys guide and the collimation pamphlet that came with my scope for collimation.. the collimation looks spot on as advised by the two sources.. ill try posting an image thru the focuser soon.. but as soon as i step out.. while trying to focus any bright object like jupiter.. i can see oval discs as i move from one side of the focus to another.. thats telling me that the collimation is still not spot on..

2. @umadog.. the stock 28mm EP.. i think its only a single-element EP, even though the closest match i found online states its a 3-element design.. and it shows visible darkening.. if my eye slides off to one side even a little.. i get darkening near the opposite edge of the view.. the EP has an eyecup that screws into and out of the EP.. i usually have to extend it fully so my eye stays near the axis of the EP.. the same is true for the 9x50 finderscope.. @ronin.. the EP is 2".. heres the closest match i found online.. mine is identical to this one.. Skywatcher LET 28mm - 2" eyepiece, 55° FoV - OCCASION..

3. @umadog.. coma / hyperions.. thanks.. now that was good info.. atleast i know now to stay away from hyperions.. i didnt know that coma might not be a severe problem at higher mags.. i was gonna get a coma corrector but now id save that cash for EPs.. =)..

4. @umadog.. hand-held camera.. yea mate i know its a disaster but i was confused if the blurring is cuz of the collimation or camera shake.. i guess id have to wait till i get a mount and an adapter before i can pin the problem.. @ronin.. yes brother i know thats the stupidest thing anyone can do.. but i cant wait till i can get my hands on a mount or an adapter.. im gonna get them soon though.. =)..

5. @umadog.. EPs.. i knew wide-field EPs were expensive but i also thought the very short EPs (~5mm) are also expensive.. but your response comforts me that i might get away with a semi-cheap short plossl or something.. =).. on the contrary.. i cant buy or sell second hand.. there isnt any second-hand market in pakistan.. heck.. there isnt even a first-hand market.. i have to order from germany or norway and have a friend bring it over to pakistan for me.. so whatever i buy ill have to keep for a very long time.. =(

6. @ronin.. exposing jupiter.. 30 seconds? im think youre assuming a high magnification which would dim the image.. cuz i tried exposing jupiter last night and i found that 1/8s was enough to detect the moons as dots.. and 1/200s was enough to expose the planet's disc without clipping the colors to white.. i wasnt using any EP..

7. @ronin.. neq6.. yea i dont have any mount yet.. i ordered the kit in parts as much as my funds allowed.. got the OTA first.. now gonna get a mount.. along with some EPs and a barlow etc..

8. @ronin.. EPs.. actually i was thinking about getting a 2x barlow.. and 3 EPs close to 32mm, 12.5mm and 5mm.. this will give me a mag set of 31x, 63x, 80x, 160x, 200x, 400x.. i know 200x and 400x is a lot.. but i should be capable of getting upto 400x in stable atmospheric conditions.. even a bit further up.. what do you think? i cant be ordering EPs one at a time.. since my friends dont come often from abroad.. next time they come might be more than a year away..

9. @ronin.. registrax.. yes i dont have a webcam.. im using a nikon D90 to create an AVI.. one thats as stable as possible.. when using single jpegs, i use the burst mode on the camera.. snapping some 100 or so pics with little movement between them.. still the end results arent any better than the initial images.. often worse.. so much so that ive resorted to using AVIStack v2.0 instead of registrax..

10. @ronin.. dob mount.. yes mate i think thats the best piece of advice.. gotta make a mount till i buy one.. hand-holding is just stupidity.. =)..

thanks a lot you two.. =)

as a last question.. im buying from Teleskop Express store.. what EPs, barlows, filters do you guys recommend from here? i need only 2 or 3 good EPs (4mm, 11mm, 32mm), a barlow maybe, and a UHC filter maybe.. i have the budget of around EUR100 max per item..

im sorry if it looks like i want everything done for myself.. but ive looked around a lot and asked a lot of questions earlier on too.. but i just cant decide on what to buy cuz i have little idea and experience.. and there are so many to choose from.. with so different prices that i go crazy.. =(.. ive looked primarily at TeleVue, SkyWatcher and TS Optics EPs..

please help..

[John]

Jupiter is a slight oval of course but "oval disks" as you move through focus sounds odd to me. If the oval switches orientation as you go through focus then it could be astigmatism within the scope optics - there are examples of this on this web page:

Basic Star Testing

If the ovals stay the same orientation then it could be that the secondary mirror is not square to the focuser.

I doubt your 28mm is a singlet lens unless somebody has stolen one of the lens elements !. It will most likely be a Kellner-type design which has a singlet field lens (bottom lens) and a doublet eye lens. They are OK to get you started but not much more than that.

On eyepieces, the choice is huge and everybody has their favourites but Tele Vue's are all designed and individually tested to be sharp down to F/4 so would be a good bet if you don't want to take any risks.

I use a decent 10" newtonian but have never used anything like 400x with it. Even 300x is only very rarely used so you might want to consider how much you invest to obtain those sorts of powers if your budget is tight. Of course you may encounter superb viewing conditions more often than I do.

[umadog]

I really don't think you have a single element design. That would be just one lens. It wouldn't even be called a Plossl. I used to have a low-power 3-element eyepiece and it was awful. Replace yours with something better.

The darkening you're talking about sounds normal to me. I wouldn't worry about that.

Coma is worse at the field edges and is bad/noticeable only at the edges of the *true* field of view. I've forgotten how to calculate the affected area, but the idea is that magnifying more shows you less of the true field of view and so you see less coma. I remember it wasn't a problem on my old f/5 when I went up to about 80 or 100 x and above.

Faster scopes produce a steeper light cone entering the eyepiece and so light is being bent by larger angles. Defects in the eyepiece's design are more likely to show up under these circumstances. So eyepieces that are cheaply made or not well designed may show astigmatism at faster focal ratios. They will all show coma. Astigmatism tends to occur in the outer regions of the field where light is being bent the most. Consequently, astigmatism is often mistaken for coma. The Televue Plossls are corrected for faster scopes so they could be one option (I think they have a 5th element in them to achieve this). As a rule of thumb, more elaborate (i.e. expensive) eyepiece designs will work better, but you will still see a marked improvement over your stock Plossl were to replace with a better Plossl. This may be the cheapest route initially.

Eyepieces with shorter focal lengths have less glass in them so they're cheaper because they're easier to make and require less glass. Eyepieces with more elements in them cost more. Eyepieces with the wide apparent fields of view cost more because they require expensive high-index glass. The most extreme I've seen is this sucker: Explore Scientific 9mm 120° field waterproof 2" eyepiece EPWP12009-01. Costs a grand and you get 120 degrees of apparent field of view. Not been released yet, though.

I have used a coma corrector at f/5 and it does make a noticeable improvement to the image at lower powers. The only reason I bought it, though, is because I was expecting an f/4 to be delivered over the next few months. Right now I'm also using an f4.8 without a coma corrector (for weight reasons). The stars don't look quite so pretty at lower powers, but you get used to it pretty quickly.