DanielC

Thanks for all the help guys! This is very helpful. I'll follow @Second Time Around's advice and get a zoom eyepiece, and I'll follow @John's advice and add a low power eyepiece for wide angle. I haven't bought the telescope yet because it's out of stock, but I'm planning to get a Celestron NexStar 6SE. So if the zoom shows a good image at 8mm and it looks stable enough, I could add a 6mm later. But I'll first wait and see how the zoom works out.

Thanks again!

What are your thoughts on zoom eyepieces? In what situations do you think they're a good option vs fixed eyepieces? For example, I know that zoom eyepieces typically have a smaller AFOV than fixed eyepieces. Is that their main disadvantage? I read online that zoom eyepieces can be great for planets because there's usually one particular magnification that really works a lot better than the others in terms of making features large enough while still having enough contrast, and that.

Looking at prices, I'm thinking that if you just get a zoom eyepiece you can spend more money on it than if you buy several fixed ones. For example, for a $200-$250 budget I could either buy...

• Four Orion Expanse Wide-Field 1.25" Eyepieces, OR
• Three Orion EF Widefield 1.25" Eyepieces, OR
• One Orion 8-24mm Pro Lanthanum Zoom Eyepiece, OR
• One Celestron 8-24mm Deluxe Zoom Eyepiece.

To my inexperienced eyes, it looks to me like I can a cool and fancy zoom eyepiece for the price of 3-4 regular eyepieces and I'm trying to figure out if that's a good trade.

Thanks for the help!

12 hours ago, Louis D said:

If you pair the 40mm with a nebula filter such as an OIII, the larger exit pupil may make the nebula appear brighter than it would with the 32mm.  This is especially important with longer focal ratio telescope such as CATs that produce small exit pupils with most eyepieces.  For example, to get a 6mm exit pupil with an f/15 Mak would require a 90mm eyepiece. 😲  Good luck finding one of those.

Thanks. Can you help me understand this? For the SCT that I'm planning to buy, the focal ratio is F/10 so the exit pupil is 

pupil = (focal length of eyepiece) / 10

So the 40mm eyepiece would give me a 4mm exit pupil and the 32mm eyepiece would give me a 3.2mm exit pupil. So I googled for "exit pupil" and I saw that apparently a larger exit pupil means that there's more light going into your eye. But I don't understand that. If both eyepieces are already at the maximum field of view that the telescope can produce, aren't they both giving me every last photon that the telescope can collect?

Thanks!

14 minutes ago, Kyle Allen said:

A 32mm Plossl with a 52 degree AFOV will show the maximum area of sky possible in a 1.25 inch format. Longer focal lengths will yield less magnification but won’t show any more sky, unless you move to the bigger 2 inch format.

The larger AFOV will be more comfortable to look through and feel less restricted even though you are seeing the same area of sky.

The only reason I can think of for going for the 40mm would be to get a bigger exit pupil in a very slow scope like a Maksutov that is limited to 1.25 inch eyepieces. 

Thanks!

Let me add that Jupiter and Saturn are actually difficult targets. I know everyone wants to see Jupiter and Saturn, but they're tiny and it's hard to see anything besides a small fuzzy circle. In general, planets are hard because they're small, and nebulae are hard because they're dim. The easier targets (after the moon) are globular clusters and binaries. Go back to your friend and ask him to show you some of these:

1) Double Double -- it is a 4-star system (two binary stars in orbit around one another).

2) Mizar & Alcor -- binary in the Big Dipper; if you zoom in you'll see at least one more star. In truth, Mizar & Alcor are really a 6-star system.

3) Albireo -- a beautiful binary; one bright red and one dimmer bluer star.

4) Great Cluster in Hercules -- globular cluster

Then you'll have more information about what's possible with a telescope.

On 19/07/2020 at 11:15, Nigeyboy said:

Hi all

I have a rare opportunity to go out tonight to try and see Neowise among other things! I live in Derby and was planning on driving out through Ashbourne toward Buxton. Can anyone recommend a place for me to go that had wide visible horizons, while being away from LP? 

Thanks in advance

Nige

I don't know your area, but here's a light pollution map:

https://www.lightpollutionmap.info/#zoom=5.10&lat=6590529&lon=-151987

3 hours ago, galaxy-gazer said:

With reference to my earlier post about in dilemma of choosing a new telescope, seems like it that I might have to choose. 6” purely due to lack of funds and off course storage.

which 6” reflector would you guys recommend?

dobs or eq2 mount?

I am no expert, but I'll jump in because I also set out to find a 6'' reflector. The problem that I found is that an eq2 mount would be unstable unless you spend a fortune on  a very solid one. A dobs would be stable and cheap. In the end I didn't go that way because my partner didn't want a dobs because they're bulky, so we decided to go for an SCT instead of a reflector. The SCT costs more money than a dobs, but not as much as a reflector with an eq2 mount strong enough to hold it steady.

3 hours ago, galaxy-gazer said:

focal length 1200 or 700?

For a 6'' = 150mm aperture we get:

FL = 1200 -->  focal ratio = F/8

FL = 700 --> focal ratio = F/4.67

I have been advised that a focal ratio around F/5 is very difficult to use because the image goes out of focus very easily, and you may need to spend a lot of money on an expensive eyepiece just to get the F/5 to work. I have been told that it's better to go for a longer focal ratio (so in this case, F/8) because it's easier to use and a less expensive eyepiece works just fine.

3 hours ago, galaxy-gazer said:

this will help me narrow down to a few!

thanks in advance to everyone out there!

 

Hi everyone.

I'm trying to pick a wide field eyepiece and I'm looking at these two:

• 32mm Meade Series 4000 Super Plossl 1.25" Eyepiece, AFOV = 52.0°
• 40mm Meade Series 4000 Super Plossl 1.25" Eyepiece, AFOV = 44.0°

I plugged both of these in the Field of View Calculator, paired with a Celestron NexStar SE6, and they seem to have a near identical field of view:

So... what's the difference between a 32mm with a 52° AFOV and a 40mm with a 44° AFOV?  If they cover the same real field of view on the sky, wouldn't the 32mm with a 52° AFOV appear larger when you look through the eyepiece? I thought that a 40mm would always look more zoomed in than a 32mm but maybe it's not that simple. Can someone clarify this for me? And also, in this example why would anyone choose the 40mm over the 32mm? It looks worse in every way.

Thanks for the help!

So a few days ago I decided to buy a Celestron NexStar 6'' but since they're out of stock right now, I'm aimlessly skimming over telescope websites and I saw that Celestron has two other telescopes that seem to be closely related to the NexStar:

• NexStar 6SE ($800)
• SkyProdigy 6 ($1,000)
• NexStar Evolution 6 ($1,300)

Can anyone help me understand what the other models have that make them more expensive and whether the price is worth it? As far as I can tell the specs of the OTA itself are nearly identical. But there seem to be several differences in the mounts:

• SkyProdigy says has a "fully automatic alignment procedure" and you can see a little camera attached to the mount. From the description, it seems to me like the SkyProdigy uses that little camera to take various pictures of the sky to orient itself. That's cool I guess.
   
• SkyProdigy seems to have a flimsy mount: 8 lbs capacity (exactly the weight of the OTA!). The tripod weighs only 5 lb.  For comparison, the NexStar holds 12 lbs (tripod weight = 9 lbs).
   
• Conversely, the Evolution is sturdy: 25 lbs capacity (tripod weight = 11 lbs).
   
• Evolution has built-in wifi, integrated Lithium-ion battery, and two eyepieces instead of one.

So... the SkyProdigy looks flimsy which is weird for a more expensive telescope; and the Evolution looks great, but is the difference really worth another $500? Is there anything about these telescopes that I've missed that help justify their prices?

Always grateful for any help.

On 19/07/2020 at 00:55, Seon tuscano said:

India could u suggest me about my career and different options??!!

What is your idea of "space science"?

• Building rockets and satellites? (i.e. space engineering)
• Observing galaxies and nebulae? (i.e. astronomy)
• Moons of Jupiter, craters, etc? (i.e. planetary science)

How good are your grades? Are you good at math and do you like math?

I am not familiar with the Indian school system. What is 12th science?

Let me start by saying that all the things I listed (astronomy, planetary science, space engineering) are all things that India does, but they are all small fields and very competitive. So in all cases the strategy would be to pursue a career in university that gives you the opportunity to go into those disciplines but also keeps options open in case that plan doesn't work out. This won't be difficult at all because all the things that truly specialize those disciplines are things that you'd learn later in your career. The main goal should be to keep doors open:

• In all cases you would need to study math and classical physics. Very important.
• You have to either teach yourself how to program or take a course. Try to find a course targeted toward science students rather than "computer science".
• If you want to pursue space engineering you need to look into engineering courses.
• If you want to pursue astronomy, some astronomy courses would be helpful.
• If you want to pursue planetary science, you might want to take a geology course, and at least first year chemistry.

If you give me more details, I can help you more. I am an astronomy postdoc at a university and I'm familiar with some of the options.

2 hours ago, Cosmic Geoff said:

I never found the cooling time a serious problem with my C8 SE.  One can view less demanding targets first.

  A dew shield is an essential accessory.  If you don't want to buy a smart-looking plastic one, you could make your own shield.

Ok. Dew shield.

Is a light pollution filter a good investment or is it a waste for money? I live in a suburban area, and I won't be doing astrophotography.

EDIT:  I just thought of another question. Do you collimate SCTs? Or is that something you only have to do for Newtonians?

7 hours ago, vlaiv said:

In that case, how about this one:

https://optcorp.com/products/celestron-nexstar-6se

It is still 6" instrument so you won't be loosing any light grasp over 6" newtonian. It is much lighter and compact - cheaper GOTO Alt/Az mount should be able to carry it without too much trouble.

It is F/10 instrument and hence provides same focal length as F/12 Orion Apex 5" Mak - same FOV.

Only drawback is that it is limited to 1.25" eyepieces and won't provide you with wide field of view.

Perfect. I'll get this one. I saw it earlier and I liked it. I had ignored it because I had it in my mind that Newtonians were always the best value for money. But now I see that it's not so simple. The drawbacks of the NexStar 6SE look like things that I can handle better than the drawbacks of the reflector. Not getting a wide FOV is unfortunate, but not as bad as a shaky mount or low quality components; and I still have my binoculars. To deal with the dew and cooling time, I will keep the telescope in my garage, or I'll make sure to bring it outside early.

Thanks for all the help!

21 minutes ago, Cosmic Geoff said:

For your initially quoted budget you would have more choice of outfit if you go for a smaller aperture, i.e. 127 or 130mm, which is still enough to give you many nights of enjoyment, particularly if you can actually find the objects with a GoTo.  A 127mm Maksutov, unlike some of the entry level reflectors, will be a good quality instrument optically and mechanically.  It is the kind of instrument you will keep even if you graduate to something bigger.

The lower cost mounts tend, alas, to be on the wobbly side.  If you want a decent aperture telescope on a really solid mount, the total cost rockets to a wallet-emptying degree.

Three element eyepieces should be avoided.  Plossl eyepieces are adequate in many situations, particularly for longer focal ratio telescopes, while f5 Newtonians will probably benefit from a more exotic eyepiece design.  I am not an eyepiece expert though

After spending the last few hours trying to make the 6'' reflector idea work, I don't think I can stretch my budget that far. So I'm ready to consider a lower aperture and longer focal length. You gave the example of a 127mm Mak. What can I expect from an instrument like that? How do I know if I'm looking at a quality instrument? The first 127mm Mak that I found has a focal ratio of F/10.

https://www.telescope.com/All-Telescopes/Orion-Apex-127mm-Maksutov-Cassegrain-Telescope/rc/2162/p/9825.uts

Using the field-of-view tool that @vlaiv suggested, and seeing that the above telescope comes with a 25mm eyepiece with a 52deg FOV, it looks like it would work well for several Messier objects including the Crab Nebula and globular clusters, but  the FOV is too small for the Orion Nebula. If I add a 6mm eyepiece I'll see Jupiter's moons, but I'd need some luck and/or a filter to see a band on Jupiter.

I think I can work that that. I need to think a little more, but I am persuaded that a small high-quality instrument is a better investment than a large poor-quality one.

You said that a 127-130mm Mak is an instrument I one would keep even after graduating to something bigger. What would you do with a 130mm Mak if you also have a 150mm telescope? Do you have smaller telescopes that you often use?

Thanks for the help!

24 minutes ago, vlaiv said:

Under mounted scope means that one is using telescope on a smaller mount than would be suitable for that particular telescope. In the end it is subjective thing - there are no rules except weight limit of the mount (and even that is a guide line in most cases). It creates general bad experience of using scope - things get shaky and it takes long time for view to settle. Whenever you touch eyepiece or focuser - resulting vibrations take multiple seconds to settle. Sometimes it is very hard to properly focus in such conditions - you are never sure you have right focus due to motion blur of the shake.

Ah! This is all very helpful. Yes, I remember being very frustrated in the past with shaky telescopes.

24 minutes ago, vlaiv said:

Another "drawback" of this basic model is that it does not have collimation screws for primary mirror.

It comes precollimated from factory and that is it. Sometimes optics gets out of alignment and you need to adjust it - collimation. Regular newtonian scopes come with collimation screws to do that (rather simple procedure). People say it is not big deal and scope is well aligned, but I would not feel at ease owning the scope that I can't adjust if need be.

Thanks for catching that! Yeah, back when I had my small table top telescope I learned how to collimate it. It never occurred to me that a $550 telescope would not have collimation screws. I thought it was standard because my little $50 table top had them.

24 minutes ago, vlaiv said:

I would not suggest this scope for visual - it is too fast. It has focal ratio of only F/4. With Newtonian telescopes, primary aberration is coma and it depends on speed of mirror. Fast scopes will have more coma and there are coma correctors for this purpose (mostly used for photographic applications but there are a few models used for visual). Fast scopes also require more expensive eyepieces in order to have well corrected image.

If you can - look for F/6 scope for visual. F/5 is still ok but it is considered fast scope.

That's also very helpful. I will aim for an F/6 then. Going in the other direction, how much focal ratio is too much? I just saw a Maksutov-Cassegrain with F/15. I know that if the focal ratio is too high you end up with a small field of view so it's impossible to see wide things like the Milky Way. I am looking for a general purpose telescope that works fine for "everything". One day I'll try to see Saturn, the next day I might want to see the Pleiades.

24 minutes ago, vlaiv said:

If you can avoid it - don't use Equatorial type mount with Newtonian telescope. Due to focuser placement on newtonian telescopes and the way EQ mount tracks - eyepiece ends up in very awkward positions and this usually requires you to rotate telescope in rings. This gets rather tiring after a while (unlock tube rings, loosen them, rotate tube, lock tube rings ....)

EQ mounts are better with telescope designs that have focuser at the end of the tube (refractors, folded telescope designs).

Good to know. I will look for alt-az mounts then. I liked the iOptron mount that you suggested. I'll try to find something like that here.

24 minutes ago, vlaiv said:

Number of elements is important because it shows what type of design eyepiece could be and it is believed that fewer optical surfaces means more light throughput (and it was certainly so some time ago, but with modern optical coatings differences are minimal).

For first upgrade / first set of eyepieces, look at these:

BST Starguider range or Celestron X-Cel range.

Thanks!

48 minutes ago, vlaiv said:

Hi and welcome to SGL.

With that particular model, my concerns are that it will be under mounted scope and scope that is of not too high mechanical quality - rather basic model (due to weight savings).

If you like purchasing as a single package and you don't mind it being rather basic model, then yes, by all means - go for that one. Alternatively consider these...

Thanks for all the help! From what you are saying, it sounds like I might need to revise my budget and maybe also pick the components myself rather than grab a pre-packaged set so I don't get stuck with a crappy mount and crappy eyepieces. Can you explain a little more what an "under mounted scope" is? What are the downsides of a basic model compared to a higher quality one? I want to make this choice carefully because if I end up throwing away the basic model and buying the expensive one anyway then I wasted my money. You mentioned that the heavier mount would be more stable and I definitely see how that is very important. Is that the main difference? You said the other mounts you suggested were overall better quality; so what else would be different about them? Likewise, what are the advantages of the OTA you suggested? Is it mainly that it will have better optics? I can see that it has a 2'' focuser so I could buy a wider field eyepiece and take a huge picture of the galaxy.

I think I can find components similar to what you suggested:

1) OTA

https://www.telescope.com/All-Telescopes/Orion-6-f4-Newtonian-Astrograph-Reflector-Telescope/rc/2162/p/116530.uts

This is a 6'' Newtonian reflector that looks very similar to the one you suggested. I found it in the "Astrophotography" page.

2) Mount -- version 1: equatorial, not GoTo

https://www.telescope.com/All-Telescopes/Orion-SkyView-Pro-Equatorial-Telescope-Mount/rc/2162/p/9829.uts

This mount says it can handle 20lbs and the telescope above weighs 12.7 lbs. So I guess it must be a sturdy mount. But there is no GoTo.

3) Mount -- version 2: equatorial + GoTo

https://www.telescope.com/All-Telescopes/Orion-SkyView-Pro-Equatorial-GoTo-Telescope-Mount/rc/2162/p/24709.uts

This is the same mount as before, but with GoTo included.

4) Eyepieces

https://www.telescope.com/All-Telescopes/Orion-Expanse-Wide-Field-125-Eyepieces/rc/2162/e/55.uts

I don't know anything about eyepieces, but these ones say 4-5 elements (why do I care how many elements it has?), the opening looks much larger than the cheap eyepieces I saw earlier, the eye relief is 15-18mm which sounds like a lot to me.

Do these look similar to your suggestions?

Let's see... my initial suggestion was $550 and the combination above would be $800 - $1,200 depending on whether I get the GoTo. I also found an 8'' Dobsonian alternative for about the same price. So I need to take this information and think a bit more.

Thanks for the help!

Hello everyone,

I am a professional astronomer who is embarrassingly bad at backyard astronomy. I have two pairs of binoculars that I use infrequently. I used to have a table top 4'' telescope, and when I was a grad student I did sky tours for the public. So I know the basics. I recently decided that I want to buy my own telescope for personal use. I think I have narrowed it down a 150mm reflector with a GoTo mount. My prototype for what that my look like is the Orion StarSeeker IV:

https://www.telescope.com/catalog/product.jsp?productId=113917

I was hoping someone could help me figure out whether this is a good choice and whether there's an alternative that I should be considering. I live in a suburban area with a fairly polluted sky --- lightpollutionmap.info says that my location has SQM = 19.6 which apparently translates to Class 5 in the Bortle scale. I also have relatively poor eyesight, even with eyeglasses. So here are some concrete questions that I hope someone can answer:

• Am I right to think that a GoTo mount would be especially helpful in a light polluted sky? I'm thinking that star hoping could be difficult.
• What do you think I would realistically be able to observe with a 150mm telescope from my location? Would M31 look like anything more than a tiny fuzzy blob?
• The website above says that the Orion StarSeeker IV comes with "3-Element" eyepieces. Can someone tell me what the heck that means? Is that a brand? Are they ok?
• Anything else I should know?

Other considerations: The telescope above is around the maximum price / weight / size that I think I can handle. I know that I could get a bigger aperture for a lower price with a Dobsonian, but I want to keep it small enough that I could realistically take it on a road trip to a national park once a year, and my spouse is keen to have the GoTo mount.

Thanks in advance for the help. Cheers!