Orion ShortTube 80mm vs StarBlast 90mm

[sekelsenmat]

Hello,

I am just starting with astronomy and deciding on my first telescope. I already learned to recognize most constellations, I can find Andromeda Galaxy with a binocular, etc, but I never owned a telescope. I live in a city center with heavy light polution, so I need a scope that will be:
1> Light and small, so that I can take it me on trips. Note that most of the trunk in any trip will be filled with baby stroller, baby dippers, etc, and sometimes I travel by airplane, so the smaller and lighter, the better!
2> Price max USD 300-400 should be ok, including tripod.
3> Flexible, so that I can add a sun filter, change the eyepieces, connect to a camera, etc
And the objects that I want to see are:
1> Saturn, Jupiter, Mars, Venus -> I'd like to see something like the right-side image here, even if only after taking video and stacking: photo
2> Messier objects, Albineo
3> The Sun

Based on my requisites I decided that it needs to be:
1> Refractor because it is smaller than an equivalent Reflector
2> 80mm to max 100mm
3> AltAz tripod because it is lighter than Equatorial

So I came up with two possible scopes that attend all my requisites:
1> Orion ShortTube 80-A
2> Orion StarBlast 90mm

Now, my great doubt and question is:

1> The ShortTube is almost half the length of StarBlast, which is a definetively huge plus in mobility and traveling. But images I saw of saturn using it are quire underwelming, like this video. I can't easily find photos shot with the 90mm so it's hard to compare. So is the 90mm much better for viewing Saturn/Jupiter? I can accept that I will need to take photos and stack them to get a half-decent result, but buying a scope in which even after stacking the result would be just almost uniform balls would be really bad. That's why I wonder how much more detail the 90mm would give and if it is worth the extra weight?

But I also have some Secondary questions:

2> The ShortTube doesn't come with an altaz tripod, which cheap and good tripod to buy for it?

3> Any recommended sun filters for use in each of those?

4> The 90mm comes without a finder scope, any recommendations of one that would easily fit?

5> For shooting photos, any recommendations if I should just buy an iphone adapter or if it really needs to be a camera? USB cam is probably a no-no since I would need to take my laptop along which would decrease mobility.

6> Is a 3x Barlow a good addition for planet viewing?

7> What is the point of the "9mm Expanse Widefield EP" and is it really worth buying? 

thanks in advance!

[Putaendo Patrick]

Planets are always small objects with amateur telescopes and you will never see the close-up detail of images from the Hubble space Telescope etc which are often illustrated in books and magazines. I generally use magnifications in the x120 to x200 range.

The maximum magnification is limited by two factors; the telescope itself and the prevailing atmospheric conditions where you observe. As a rough guide, the telescope's maximum is double the aperture in mm. This an 80mm will give x160 and the 90mm will give x180 maximum. Atmospheric conditions in the UK for example often limit you to about x200 maximum - but this will depend where you are.

Focal length will determine the magnification of any particular eyepiece, with longer focal lengths giving more power. For example, a 10mm eyepiece in a 400mm scope will give x40 while in a 660mm scope it will give x66. To get the maximum x160 from a 400mm focal length Orion Short Tube 80, you will theoretically need a 2.5mm eyepiece and this pushing it. To get the same x160 magnification with the 660mm focal length Orion Starblast 90 you will need a 4mm eyepiece, which is a little more reasonable.

Even so, neither scope is ideal for planetary observation. For a very compact telescope with a longer focal length, you might consider a Maksutov. This is a catadioptric design which combines both lenses and mirrors. For example, https://www.firstlightoptics.com/maksutov/skywatcher-skymax-102-eq2.html  or the smaller 90mm version, although I would recommend an Alt-Az such as the AZ3 mount over the EQ-1 in this case. The focal length is 1300mm which will be better for planets - but the disadvantage is a narrower field of view, which is not so ideal for low power views. Unfortunately there is no telescope which is perfect for everything, so you have to prioritise your principal interest.

Some of your other points: a Barlow is more glass in the optical chain and if this is poor quality it will degrade the view. Personally, for visual observation, I would stick to x2 or x2.5 but this depends on the make (and price).

For solar observing, you will need a filter which fits completely over the front of the telescope. This can be glass or special mylar film, and there are versions for visual and photography which are NOT interchangeable. You can buy this ready made or buy sheets of film and make your own. This will allow safe basic solar observation. There are other types of  specialist filters which will pick out other details but these are seriously more expensive!   Don't forget to completely cover or remove your finderscope - or make a small filter for it from the same film. .http://astrosolar.com/en/

Astrophotography is a whole speciality, and can be a very expensive hobby. Normally you will need a solid (i.e. heavy) mount with go-to or motors which will track objects as they "move" across the sky. However, you can get good results with a cellphone camera on brighter objects such as the Moon and planets. I'd start off experimenting with the iphone adapter.

There are several types of finder which either have magnification or don't. Telrad (quite large) and Rigel (smaller) don't but are very effective in getting you to the general area of an object. Another type of finderscope is the RACI (right angle correct image) which magnifies and shows the sky as you see it normally. Some people use both in combination, although mounting both of these on a small scope isn't so easy.

Perhaps the most compact and light weight tripods for travel with a small scope are good photographic tripods. There are special Alt-Az adapter heads available for astronomy but, beware, these can be quite expensive.

 

[Louis D]

I recommend you read this recent thread and this one as well.  Lots of collected thoughts in them both related to compact first scopes.

I have had an ST80 for nearly 20 years and rarely used it because the correction is so terrible (lack of sharpness and tons of chromatic aberrations).  I recently bought an AT72ED and love it.  It is sharp and has very little CA.  It started out light, but to keep it steady, I upgraded the mount, tripod, diagonal, etc. to get the most out of it.  The whole thing still takes up very little trunk space when collapsed.

[BGazing]

On 14/09/2016 at 11:42, sekelsenmat said:

2> Price max USD 300-400 should be ok, including tripod.

 

@Louis D directed you to one of the threads where I have sought advice on a very mobile setup from those who are much more knowledgeable than I am. Nevertheless, I feel like I can chip in on this particular point and - please - do understand that this is not pushing you to spend necessarily more money. One can enjoy the skies with naked eye, or binoculars, or whatever...

I am not sure that 400 USD in total will give you a satisfactory tripod, mount and tube for the long term. That's around 350 euros. The complete packages sold at that price are usually seriously undermounted and you will not enjoy it, and will either exit the hobby or spend double the cash to finally get something you enjoy. For a couple of hundred euros more you can seriously improve the long-term viability and enjoyability of your purchase, especially if you snatch a second-hand ED doublet in the classfields. At 400 USD a dob is a better buy than a refractor setup, methinks...

[Louis D]

2 hours ago, BGazing said:

@Louis D directed you to one of the threads where I have sought advice on a very mobile setup from those who are much more knowledgeable than I am. Nevertheless, I feel like I can chip in on this particular point and - please - do understand that this is not pushing you to spend necessarily more money. One can enjoy the skies with naked eye, or binoculars, or whatever...

I am not sure that 400 USD in total will give you a satisfactory tripod, mount and tube for the long term. That's around 350 euros. The complete packages sold at that price are usually seriously undermounted and you will not enjoy it, and will either exit the hobby or spend double the cash to finally get something you enjoy. For a couple of hundred euros more you can seriously improve the long-term viability and enjoyability of your purchase, especially if you snatch a second-hand ED doublet in the classfields. At 400 USD a dob is a better buy than a refractor setup, methinks...

Buying used is how I put together my refractor rig.  $200 for an AT72ED, $110 for a DSV-1 mount, $130 for a Manfrotto 058B tripod, $75 for a dielectric 2" diagonal, and $6 for new old stock Sorbothane insole to cut into vibration damping pads.  I bought a new 8" dovetail bar for $30 to complete the setup.  All together, about $550.  A bit above your price point, but it is rock stable, smooth in motion, and very well corrected.  It helps to know what to look for and snatch it up when it becomes available at the right price in astro classifieds (most of the items), Craigslist (the tripod), ebay (the insoles), etc.

I started with an ST80 on a micro fluid head and couldn't stand to use it for over 15 years due to its poor optics (it's an f5 achromat) and lousy motions (kept flopping backward at high inclinations).  I haven't sold it because I keep hoping to find a good use for it.  Maybe as an outreach refractor for newbies to mess around with?  My point is, if the telescope doesn't giving pleasing views or is a pain to use, you won't use it; and you've basically wasted your money.  Resale value on such scopes is usually quite poor.  Invest in a good used scope, and you should be able to get at least your money back later if you ever sell it.

[BGazing]

we also have to factor in that the us second-hand market is fabulous. eu market? not that good, and the OP might have a much narrower field to chose from, although being located in the EU will help as long as he is able to trawl astro forums in several languages (german, french, dutch, etc.).

[Louis D]

1 hour ago, BGazing said:

we also have to factor in that the us second-hand market is fabulous.

I guess Americans are a fickle lot.  Always trying to find just the right thing and selling that which doesn't measure up.