planetary eyepiece suggestions

[ian_j_kirk]

Hi everyone, after a little advice please. Im looking to expand my ep collection and would like an ep to view the planets, especially now Saturn is visible again. My scope is a skywatcher skyliner 8" dob with focal length of 1200 mm (f6). My budget is about £120 so what would people suggest? Clear skies. Ian

[nightfisher]

i would be thinking some sort of orthoscopic for planetary, maybe a couple of baader classic ortho`s from FLO but do you wear glass`s? if so then ortho`s might not be the best option

[ian_j_kirk]

Thanks Nightfisher, no I don't wear glasses so that wont be an issue. What makes orthos good for planetary viewing? Do they produce sharper images, more contrast or a larger image in the eyepiece? Sorry for all the questions but im somewhat of a newbie. Thanks. Ian

[nightfisher]

no problems for the questions, its how you find out things

orthoscopics are regarded as planetary EP`s they generally have a very sharp image, but a some what narrow field of view, that is okay for planets and lunar surface, they wont produce a larger image as this is just a ratio of scope focal length divided by ep focal length, so a 10mm ortho will give same image size as a 10mm plossl if you see what i mean.

The ortho is a simple ep with just four glass elements, they give really good sharp image with a neutral colour tone

[andrew63]

I see you have a BST 18 - if you are pleased with that a 8mm in the same series could be a good option.

andrew

[nightfisher]

the 8mm BST is an option, but i find for planetary work the ortho`s tend to be sharper

[ian_j_kirk]

Thanks both for your responses. Just looking at FLO's website now. Whats the difference between the genuine orthos and the classic orthos apart from the price and the genuines being discontinued now? Thanks. Ian

[foundaplanet]

the 8mm BST is an option, but i find for planetary work the ortho`s tend to be sharper

Can't argue with this, he's right, they are.

I would though point out that they do have a narrow field (45') of view and as you are dobbin you will barely get a rest. I have used ortho's in my dob and whilst they are great they are also a lot of effort to keep on tracking the object. I don't mind this to much but I feel ortho's are more suited for use on an EQ mount. I am not in a position to be able to offer you advise on an exact type of eyepiece though I would recommend you look for something that has a field of view around 60' or greater.

[nightfisher]

the genuine orthos were the bees knees, but the classics are said to be very nearly as good, there is also the new Hutech orthos, about the same as the genuine but with less fancy lettering on the housing

[foundaplanet]

Thanks both for your responses. Just looking at FLO's website now. Whats the difference between the genuine orthos and the classic orthos apart from the price and the genuines being discontinued now? Thanks. Ian

Not a great deal from what has been said about them apart from them not quite as cool. You could keep your eye out for a second hand circle t ortho, these go now for around £35 and do appear on abs. They are very good value for money and on having compared one with a BGO there is only a knats between them.

[rowan46]

the ortho's will be the best bet for your price new but foundaplanet is right you will need to get good at tracking with an ortho at high power if you can find a second hand radian for about £100 that might be a better option

[Qualia]

Loads of sound and really great advice here, Ian and I cannot really add much to the topic.

I have noticed that when it comes to planetary viewing slight changes in the focal length of eyepieces makes a difference to what can be tweaked from the given object. In terms of general useful magnification, I have a little collection of EPs which run the following parameters:

• f/10: 200x, 166x, 142x, 133x, 111x, 100x, 83x.
  
• f/5: 250x, 208x, 178x, 166x, 138x, 125x, 104x.
  

For Lunar work, all these magnifications offer up something to be amazed by. The low power help frame the Moon, the mid-range frames craters and seas and mountain ranges and the high-power tweak out subtle features like terraces, tiny craters, ray grazes etc.

For Jupiter, I have used mags between 140x to about 180x.

For Saturn - I have found 140x to 200x useful mags to play around with. I'm sure one can go higher here, but a lot will depend on the night's atmospheric conditions.

Mars. The way I look at is that Jupiter is about 3x the size of Mars and to see Jupiter nicely is, say, at around 150x which means that for me to get a 'similar' view of Mars I need 450x. Well, I'm just not going to get that kind of viewing quality. So, I figure a compromise is needed, say, around 250x which still means seeing conditions will have to be very good. As such, I haven't found Mars a particularly giving planet.

Other than that, in general, try to view the given object as close to the zenith as possible and bear in mind that as a general rule of thumb the brightness of an object will decline as you up the magnification. If I up the mag twofold, say, I'm reducing the image brightness by a factor of four. If I keep on doing this eventually details just disappear.

On the other hand, increasing the mag does make detail more apparent, so, as you can appreciate, we're now at a trade-off: will increasing magnification gain more detail even though I'm making the object fainter?

I've found that playing around with this trade-off - dependent on the evening's seeing (LP doesn't really affect planets) - does make a difference. Even as little as 1mm increase or decrease in the mag - about 10% to 15% difference of magnification - can be quite surprising which is the main reason why most planetary observers will have quite a run of high-mag EPs.

For planetary work I use Orthos and in particular those that were made by Baader - the Baader GOs which are no longer in production but regularly crop up on the secondhand market from anything between £50 to £100. The quality of image in these EPs is probably almost as good as it gets. Hutech's are said to be identical in quality and by fortune FLO are selling them. If you want a similar quality image EP but with a wider field of view and perhaps a more comforting eye-relief (I haven't had any problems with the BGOs) you're going to have to spend a far bit more and perhaps ultimately delve into something like a Pentax or Tele Vue.

Yet, within reason, any quality EP that produces sharp, on-axis views will do a very nice job at planetary viewing, but most dedicated folk would agree that within this department, a decent Ortho is hard to beat. The Ortho route might be termed the 'purist-route', where the least number of glass elements is used to reduce interference and hopefully - all thinks being equal - render a brighter image. Unfortunately, Orthos have small eye lens, so eye relief can be a tad tight for some, and, again, AFOV is usually quite slight at 45 degrees or so.

It is for this reason, for example, that many other people prefer to choose wider field EPs for their planetary viewing, for hopefully, with these type of EPs, eye-relief is more comfortable and due to the larger AFOV, one doesn't have to be constantly turning their slow motion controls or nudging their dob scope. So, again, from this perspective there's nothing wrong with using a quality, wide field for planetary.

The first thing I'd say, then, is that the eyepiece best for planetary is the eyepiece that caters for how you enjoy viewing.

Final thought, whenever possible try to sit with your given object for a peaceful twenty to sixty minutes or so and you'll find that they'll be moments of great clarity and seeing. By practicing this attentive sitting you come to notice more and more detail from the given object.

[rowan46]

Loads of sound and really great advice here, Ian and I cannot really add much to the topic.

I have noticed that when it comes to planetary viewing slight changes in the focal length of eyepieces makes a difference to what can be tweaked from the given object. In terms of general useful magnification, I have a little collection of EPs which run the following parameters:

• f/10: 200x, 166x, 142x, 133x, 111x, 100x, 83x.
  
• f/5: 250x, 208x, 178x, 166x, 138x, 125x, 104x.
  

For Lunar work, all these magnifications offer up something to be amazed by. The low power help frame the Moon, the mid-range frames craters and seas and mountain ranges and the high-power tweak out subtle features like terraces, tiny craters, ray grazes etc.

For Jupiter, I have used mags between 140x to about 180x.

For Saturn - I have found 140x to 200x useful mags to play around with. I'm sure one can go higher here, but a lot will depend on the night's atmospheric conditions.

Mars. The way I look at is that Jupiter is about 3x the size of Mars and to see Jupiter nicely is, say, at around 150x which means that for me to get a 'similar' view of Mars I need 450x. Well, I'm just not going to get that kind of viewing quality. So, I figure a compromise is needed, say, around 250x which still means seeing conditions will have to be very good. As such, I haven't found Mars a particularly giving planet.

Other than that, in general, try to view the given object as close to the zenith as possible and bear in mind that as a general rule of thumb the brightness of an object will decline as you up the magnification. If I up the mag twofold, say, I'm reducing the image brightness by a factor of four. If I keep on doing this eventually details just disappear.

On the other hand, increasing the mag does make detail more apparent, so, as you can appreciate, we're now at a trade-off: will increasing magnification gain more detail even though I'm making the object fainter?

I've found that playing around with this trade-off - dependent on the evening's seeing (LP doesn't really affect planets) - does make a difference. Even as little as 1mm increase or decrease in the mag - about 10% to 15% difference of magnification - can be quite surprising which is the main reason why most planetary observers will have quite a run of high-mag EPs.

For planetary work I use Orthos and in particular those that were made by Baader - the Baader GOs which are no longer in production but regularly crop up on the secondhand market from anything between £50 to £100. The quality of image in these EPs is probably almost as good as it gets. Hutech's are said to be identical in quality and by fortune FLO are selling them. If you want a similar quality image EP but with a wider field of view and perhaps a more comforting eye-relief (I haven't had any problems with the BGOs) you're going to have to spend a far bit more and perhaps ultimately delve into something like a Pentax or Tele Vue.

Yet, within reason, any quality EP that produces sharp, on-axis views will do a very nice job at planetary viewing, but most dedicated folk would agree that within this department, a decent Ortho is hard to beat. The Ortho route might be termed the 'purist-route', where the least number of glass elements is used to reduce interference and hopefully - all thinks being equal - render a brighter image. Unfortunately, Orthos have small eye lens, so eye relief can be a tad tight for some, and, again, AFOV is usually quite slight at 45 degrees or so.

It is for this reason, for example, that many other people prefer to choose wider field EPs for their planetary viewing, for hopefully, with these type of EPs, eye-relief is more comfortable and due to the larger AFOV, one doesn't have to be constantly turning their slow motion controls or nudging their dob scope. So, again, from this perspective there's nothing wrong with using a quality, wide field for planetary.

The first thing I'd say, then, is that the eyepiece best for planetary is the eyepiece that caters for how you enjoy viewing.

Final thought, whenever possible try to sit with your given object for a peaceful twenty to sixty minutes or so and you'll find that they'll be moments of great clarity and seeing. By practicing this attentive sitting you come to notice more and more detail from the given object.

You always do that claim you can't add much to a topic then write a reference book

[ian_j_kirk]

Wow lots of great advice here, thanks everyone, much appreciated. Lots to think about. Clear Skies. Ian

[foundaplanet]

You always do that claim you can't add much to a topic then write a reference book

Always good reading 'Turn left to Spain'

[ian_j_kirk]

hi all. Just thought i would update you on which ep i went for. I got hold of a 6 mm bgo from FLO. I don't mind nudging the dob and as these give some of the nest views around i took the plunge. Thanks for all the advice and clear skies

ian

[rory]

hi all. Just thought i would update you on which ep i went for. I got hold of a 6 mm bgo from FLO. I don't mind nudging the dob and as these give some of the nest views around i took the plunge. Thanks for all the advice and clear skies

ian

i hear good things of orthos. i did think of getting a couple of them , but im dubious regarding the amount of nudging at high power. id like to hear how you find using it with your dob .

clear skies.

[foundaplanet]

i hear good things of orthos. i did think of getting a couple of them , but im dubious regarding the amount of nudging at high power. id like to hear how you find using it with your dob .

clear skies.

I don't find them to bad. I do though find it a bit of a struggle with the 5 and 6 mil with the 9 and 12 being okay. I would like to get hold of 7 though.

[Naemeth]

I wouldn't worry too much about nudging at high power. It's fine once you get used to it.

My Vixen 2.5mm LV has an AFOV of 45 degrees. So the TFOV at 260x is only 0.173 degrees. Jupiter takes about 3-5 seconds to move out of the FOV. Mind you at that power it doesn't get too much use, as the atmosphere often limits the resolution so often I just get to see a featureless blob (at worst), but when the conditions are right it's brilliant to look through.

HTH

[Qualia]

I really enjoy using my orthos and find no problem with them in either the frac or dob.

I know.

I know it sounds daft, but the planets don't move any faster in the faster scope 'Chasing' after Saturn or Jupiter is the same game on a dob mount as it is on something like an AZ4 altzimuth mount and I think if any problems do arise it is more a problem with bearings or over tightening of clutches, than anything inherently dubious in a dob mount.

Of course, the market does produce the luxury of ortho quality image with widerfield but these type of eyepieces are not cheap. In my personal experience, I would prefer using a BGO than any of the widerfields I have owned at the same magnification (Hyperions, X-Cel LXs).

[Stargazer_00]

I quite enjoy using my 6mm in a 1200mm focal length too (albeit mine is 10") for 200x. I do find the FOV a bit cramped on occasion and on those occasions I simply put in a UWA. There are other times when an UWA feels like information overload and I want to have a narrower focused FOV - this is usually when studying the moon or sunspots in white light solar. On these occasions the BGOs are very good. Always so cold on the face though, so cold.