Starblast vs. a small apo?

Hi, everyone,
I already own as Starblast and i am on a waiting list for a 90mm f/7 apo (I'm not quite sure why I did this), but I am wondering if they are redundant?
Or if one is superior to the other for viewing from an urban site?
I am highly familiar with reflectors but I have never used a small refractor.
Specifically, I am concerned that discussions on the refractor forums deal almost entirely with image quality worries, such as false color or lack thereof, and with imaging, which is not an interest of mine. I am beginning to wonder if these 80-90mm apos are primarily breautifully made collectors's items ( many of the posters to the refractor forums have several small refractors quite close in aperture) and whether the reason for this is that one can't see much through these optical jewels since they are so small, hence there is little value in posting observing reports with them?
As for my Starblast, which is well collimated, I am not too happy with the star image quality (I am used to premium mirrors) and I find that the focuser is so coarse that it's hard to get an object focus much above 50x (I am using premium eyepieces). But in theory at least it gathers a lot more light than a small apo.
Thanks for any information,
Bill Meyers

>>>I am beginning to wonder if these 80-90mm apos are primarily breautifully made collectors's items ( many of the posters to the refractor forums have several small refractors quite close in aperture) and whether the reason for this is that one can't see much through these optical jewels since they are so small, hence there is little value in posting observing reports with them?
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Bill:

You know me, I like all scopes, well almost all scopes, that Baytronix 150/1400 I bought to review ain't so hot...

Anyway, I have enjoyed an ED-80 for about a year and a half and just picked up a WO MegrezII "Fluorite" doublet to replace it, similar optics, nicer looking, better mechanicals...

A couple of thoughts...

1. There is plenty to see in these nice little 80mm APOs. In March of 2006 we made a Bonzai run in the car 700 miles to Monument Valley for a long weekend during the new moon. The only scope that went was the ED-80 and I enjoyed full nights of viewing.

I have been quite surprised at what I can see from my backyard. It is mag 4 at best directly overhead and severely lightpolluted below probably 25degrees elevation.

I was quite pleased when I found the Owl nebula and M108 in the 16 inch. Not really a surprise but I am in the middle of 5 million people who live in the San Diego/Tijuana region...

But I was really quite amazed two nights later to see the Owl Nebula in the ED-80. M76 and the the Sombero Galaxy are also fainter targets possible from my backyard.

And of course where these scope really shine is on brighter, bigger DSOs. Want to get a pristine view of th Pleiades or M-7 or the Swan??

These scopes are fun on the planets. They don't give the sort of "in your face" views a big newt will, they allow you as an observer to make the most of your skills and tease details from the planets. They also do well on double stars and will go right to the limit...

2. Compared to the Starblast... These things don't collect as much light but they probably better baffled and they put the light where you can see it. THe field of view is fully illuminated and the star quality is near perfect even at the edge. Mechanically they will put the Starblast to shame.

So, to answer your question, I certainly have enjoyed using the ED-80 over the past year and a half. I think that smaller scopes like this are best for observers with some real experience because these small scopes allow one to push the limits.

It's like driving an underpowered race car with F-1 level handling/cornering, it takes an experienced driver to make it really go. But in competent hands, watch out.

Jon

Bill,
I don't know for sure what coatings the Starblast has, but I doubt they are premium coatings. With standard coatings you will get enough light loss on two mirrors to get the 4.5" aperture down to the 3.5" (or 90mm) range in performance. Also, I don't know how large the secondary obstruction is, but subtract its diameter from the primary's diameter of 4.5". That will give you the approximate refractor size that is equivalent to the Starblast's amount of image contrast. In short, it is probably performing more closely to a 85-90mm refractor in both contrast and brightness than at 4.5" aperture. Still, I'm not blasting the Starblast (pardon the pun). I think it's a great little scope for the money, probably one of the best starter scopes out there. But your new 90mm/f7 apo, regardless of brand, is certainly going to outperform the Starblast in every category.

David E

Bill,

Considering just the 2 scopes you mentioned, with no considerations for costs, I would think it is an easy choice (regardless of urban or rural, but more so for urban).

While the 4.5" does have more light gathering power, let's remember that it's not really gobs more, but just 1.47x more than the 90mm after you figure in the loss due to the CO. Given your location you're not going to get any satisfying views of DSO even if you had a 10" scope quite frankly. That being the case we are talking a very limited number of DSO, a few more Globs, many more star clusters, then a lot of time on doubles the Moon and planets.

While I don't have a 4.5" scope I do have a 6" SCT and an 80mm refractor. Of these 2, I grab the 80mm about 95% of the time, and the 6" the other 5% just because it feels neglected. Yes I can see deeper with the 6", but given the difference in star images that the refractor puts up, I prefer to go less deep. Yes I get more resolution with the 6" on planets and the Moon, but the refractor snaps better and actually pumps higher powers better. Interestingly, both scope show their sharpest high power image around 150x in my area (lim mag 3-3.5 and Pickering 3 is the normal). However, on the same evening the 80mm can be pumped much higher with much much less fall off in image degredation. So on Moon and Planets, the 80 is actually more enjoyable.

On brightest DSO, I also prefer the 80 over the 6". Yes I get lots less light on M42 in the 80, but up at 150x I still see lots of moltiness in the nebula and the trap is gorgeous since star points are rendered so much better. For things like doubles, it's no contest that the refractor is taken out...although true that the colors are less pronounced. However, again, the difference in colors you will see given you only have 1.47x as much light from the Starblast, I'm not sure it will be significant, especially from an urban site. My 10" sure shows the colors better, but not 3x better, and it's a 10" compared to a 3 inch!!

Finally we get to the mechanicals. Night and day difference for the APO...plus I am supposing you get a 2" focuser as well. So the Starblast can get a 24 Pan in the tube showing 3.39 deg TFOV whereas the 90mm can get a 40mm Paragon showing you 4.88 deg TFOV of perfectly formed refractor star points.

Anyway, given the plus on the Starblast is 1.47x the light gathering, while the plusses on the 90mm APO are more contrasty image, better star so much images for clusters and doubles, will push more power, can get wider TFOV with 2" EPs, better mechanicals, and something you'll probably want to keep forever or hand down....I just think it's an easy choice.

-Bill

Hi:

I've tested both side by side. Which is better? Depends on what you want. The strengths of the StarBlast are its portability and its decent aperture. What I do with the StarBlast is leave it assembled on the little stand I built for it (see my Astromart review of the SB) so that I can tote it into Chaos Manor South's backyard at a moment's notice. Thank's to the little guy, I've seen some comets and other things that I probably wouldn't have looked for in our muggy, heavily light-polluted skies if I'd had to setup a big gun.

How about a refractor? An APO? I'll tell you right now that you'll probably like the images in a--for example--WO 90 or 80 or even 66 APO better than you will the images in the StarBlast. The SB, an f/4 paraboloid, demands expensive eyepieces or even a coma corrector if the condition of the field periphery is important to you.

As for a downcheck for the refractors? The WO APOs, like most similar scopes in this class, are very well built. They DEMAND a heavy duty photo-video tripod at the least (even the 66, though I can live with it on my Manfrotto medium weight rig), and are actually better on an astronomy-intended alt-az or equatorial mount. That makes 'em not quite as convenient as the SB.

In summation...if you want grab n' go with a considerable amount of aperture, and don't care overmuch about the field being "perfect," get the StarBlast. If you want a scope that's more-better-gooder image-wise _and_ can perform other jobs (guidescope, imaging) easily, look at an APO.

Unk Rod