Posts Made By: Jeremy Schmit

I'm looking at the various options for the finder scope for a 10" dob I'm currently building (finished polish-out, working on taking down a TUE). Up till now I've been fairly set on the Orion 9x50 RACI which seems to be a pretty good for the money. However, recently I've started to wonder about the Antares 8x50 RACI which is a tad more expensive. Has anyone tried both? Is the Antares worth the extra $$$? I'm also open to other suggestions, however, even the Antares is starting to push my budget (the UO RACI is definitely too expensive.) Another consideration is that the Orion finders pop up in the classifieds every few days (although they are grabbed almost instantly), while the Antares are rarely posted. This pushes the effective price of the Orion down another 20% or so. Where is my money best spent?

Thanks,
Jeremy

I'm attempting to figure a 10" mirror that is suffering from a very small (1-3mm) turned down edge. A google search on the subject has led me to try the tool on top with short strokes (my strokes are about 2" long). However, this has not had a noticible effect on the defect and my wrists and hands are getting quite sore (I tend to use a lot of pressure.) I have noticed that the center of my mirror is getting higher and higher, which I guess is a good thing cuz it means I'm removing glass, but it there something I should change so that the glass removal is 1/2" from the edge rather than 3" from the center?

thanks,
Jeremy

I'm starting to see the light at the end of the tunnel on my first atm project, so I thought I'd post some pictures here to get some feedback/suggestions/insults. It is a 10" f5.6 truss tube dob. The first picture is the assembled scope. As you can see, there are no bearings or even a rocker box yet. The trusses are still a few inches too long (and not all the same length), and the split block are only held in place by the tightening knobs. You can see my mirror polishing stand clamped to the kitchen counter on the right, and the mirror is on the floor in the testing stand just off the picture to the right.

I recently purchased one of the new Speers-waler 82* eyepieces (7.5mm), and like many other people have reported there appears to be a sizable speck of dust on one of the internal elements. I have asked the seller what I should do about this (he hasn't responded yet), but my preference would be to just take the thing apart and clean it myself and not worry about shipping it and/or getting another contaminated eyepiece. I would consider myself handy enough to undertake such a task, but I have a few specific questions:
1) Is this a REALLY bad idea and I should just forget the idea?
2) What measures should I take to keep the glass and interior clean?
3) What measures should I take to make sure I don't end up with a pile of glass and no idea what order to put the lenses back in? (I believe there are 8 elements)
4) Has anyone taken apart this eyepiece (or similar) and has advice specific to this eyepiece?
5) Is there anything else I should know/consider?

Thanks,
Jeremy

I have been working on a 10" f5.5 mirror that is my first homemade mirror, and will be my second telescope overall. The foucault tests have it coming in consistently at between 1/8 and 1/12 wave (although there are outlier data sets that have it at 1/3 wave.) These tests show the mirror as being excellent over the outer 3 inches with slightly low center starting about 2 inches out. In other words it is slighly overcorrected. Last night we star-tested the mirror, and the instructor of the class I'm taking proclaimed it done. Granted this was done as the SoCal marine layer was rolling in and the star we were using was always at least partially obscured. Tonight I took the mirror out again, and the weather was much more cooperative. Despite my limited experience star testing, I was able to easily spot two flaws, astigmatism and spherical aberation. I know that the star test is sensitive enough to reveal trivial errors, but I am concerned that if my untrained eye can see an error it must be nontrivial. When I got back home, I checked Suiter's book and I would estimate that the astigmatism is about 1/4 wave and the SA is perhaps 1/8 wave (interestingly, the star test reveals my mirror to be undercorrected, the opposite of what the foucault data predicts). For comparison, I also star tested the nearest newt I could get my hands on, a homemade 6" f5 made with an orion mirror. I have a scope made with the same mirror and can attest that these mirrors are surprisingly good. In the star test, I was unable to detect any error in the 6". My gut impression is that if my handmade f5.5 is unable to beat a mass-produced f5, I still have more work to go. However, most other people are telling me that the observed errors are insignificant. After all, I was able to split the double-double tonight. I would appreaciate any and all comments here.

Jeremy

I'm working on my first mirror (a 10" f5.5ish), and I've been on the figuring stage for what seems like an eternity. I think I have developed a pretty good feel for how to use the strokes to target specific parts of the glass, but there are two techniques that have thus far eluded me.

1) I can't even count the number of times I have ended up with a mirror that is 1/4 wave overcorrected. If I had a reliable way to target the middle zones to de-correct the mirror I would have been done a long time ago. The problem is that if I do a spherizing stroke (1/3 diameter center-over-center) the spherizing action starts at the center of the mirror and spreads outward. This means that I have to go all the way back to a sphere and start over and I loose almost a quarter inch off my focal length after every iteration (I have lost almost three inches off my focal length since I started polishing, although most of that was from fixing two badly turned edges.) Is there a better way to target the middle zones? (I would like to stay with a full sized lap as I end up with astigmatism every time I use a sub-diameter lap.)

2) I don't know a reliable way to target the edge zones. Frequently I will get a mirror that is nicely figured out to the 85 zone, but the outer 1/2" is still spherical. Usually my outer zone correction ends up happening by accident. This would be tragic if this "accident" happened during polishing, but during a 5 minute figuring session the amount of glass removed from the edge is usually just about right. However, if I have two "accidents" then suddenly I am staring at the 1/4" wave overcorrected situation again. So I guess I guess this is a two part question. First, how do I intentionally remove glass from the 95 zone of the mirror in a controlled fashion, and secondly what can I do to ensure that this is the only time I remove glass from there? (since fixing the previously mentioned TDE's my edge has been very nice. The glass I've been accidently removing from the edge has been resembled nice smooth correction rather than a sharp TDE.)

Thanks in advance,
Jeremy

As you all know, it is a bad idea to believe anything the candidates or the media says without verifying it personally. The internet is rich with information sources that cut though the campaign rhetoric and the media spin and give the raw facts. Of these sources, perhaps the most interesting and useful is factcheck.org. I know that many people on this forum are already familiar with the reliable and bipartisan reporting done by Factcheck, but I would like to once again draw attention to this invaluble resource for those who have yet to discover it. For those of you that do not have time to look through all the content in depth, I have found that virtually all of the entries fall into one of two catagories which I will now summarize for you.

Type 1:
"Recently (Kerry/MoveOn/DNC) claimed in an (ad/campaign speech/email) that the (Bush administration/economy/Iraq war) is (specific claim). This claim is based upon information from (specific source). We have reviewed this information and find that the claim is (slightly exaggerated/loaded with political spin/debated by conservative think tanks). In conclusion, we find that although the claim based on solid fact, we leave the relevance for the reader to determine.

Type 2:
The (Bush campaign/SBVFT/RNC) have accused Kerry in their latest (ad/campaign speech/email) of (specific claim) during (Vietnam/his time in Senate). They have based this claim on (specific event). We have reviewed this event and found that the republican claims are so (distorted/out of context/unsubstantiated) that in any other forum they would constitute slander. In fact, we will stop writing now before we give the republicans something else they can misquote.

(Seriously though, I am having a bit of fun here, but Factcheck does go to great efforts to present all the information in the most unbiased way possible. They are truely non-partisan, and have equally harst things to say about both sides. But I think it speaks volumes that the vast majority of their articles fit into the two catagories I have listed.)

This is a question for the pro-Bush crowd. I asked Jim this question in another thread, but I thought it would be worth broadening the question and asking the general audience.

The following is a list of events that have occured during the Bush presidency:

*The massive budget surpluses of the Clinon era have disappeared
*We are facing record deficits (in raw dollars) on a yearly basis
*The president has no plan to balance the budget (or have the budget balanced after he leaves office)
*He will be the first president since Hoover to have a net loss in jobs
*Health care costs have soared
*The Bill of Rights has been undermined
*Osama bin Laden has not been found
*The reconstruction of Afganistan has been slow and half-hearted
*His primary education acomplishment has been badly underfunded
*The president has waged a war on the environment
*He has lost the support of many of our long time allies
*World opinion of the US has plummeted
*We are facing massive trade deficits
*He has fired or removed scientists whose research disagrees with administration policy
*Gas prices have soared even after the VP put together an energy policy focusing on fossil fuels
*The country, administration, and president have been embarassed by the failure to find WMD's in Iraq
*The country, administration, and president have been embarassed by the tenuous link between Iraq and al Qaeda
*Intelligence was ignored leading up to 9/11
*We have not been "welcomed as liberators"
*The reconstruction of Iraq has come to a halt as peace cannot be reached
*The president's "coalition" has been crumbling in the face of Terrorism in Iraq
*By all accounts the situation in Iraq is getting worse
*The source of three quarters of the people and funding involved in 9/11 (Saudi Arabia) has not been mentioned diplamatically or otherwise by the administration
*Our credibility as 'benign peacekeepers' has been shattered
*al Qaeda remains a strong force (stronger even than before?)

By my count, 17-19 of these items are undisputed fact and the other 6-8 are widely held opinion (both sides of the aisle). The anti-Bush crowd will present arguements that each of these events has been the direct result of the policies of this administration. On the other hand, the president's supporters argue that the president has been 'unlucky' and these events have arisen due to circumstances beyond his control. A quick glance at the above list reveals that this has been a very unlucky president. The question of this thread is: What more has to go wrong before the president loses your vote? At what point does the list cease to be luck, and become an indication of the effectiveness of the administration?

I get the impression that the massive support of the president stems from the fact that he is a likable guy from the 'correct' political party. Because of this, his policies are defended endlessly. However, there is a growing list of mishaps. When does this list become an indictment of Bush's lack of foresight in his "It sounded like a good idea at the time" policies?

Or, does he have your vote unconditionally (well, short of building concentration camps for the extermination of left-handed people ).

At some point Bush will critisize Kerry's "inconsistent" position on Iraq. I'd like to see Kerry counter with something like this:

You have frequently accused me of supporting your war by pointing out that I voted for the autorization of force. However, at the time you said "Approving this resolution does not mean that military action is imminent or unavoidable. The resolution will tell the United Nations, and all nations, that America speaks with one voice and is determined to make the demands of the civilized world mean something." If, as you currently claim, that was a vote for war, why did you mislead those of us in congress?

(actually, if he wants to obey the rules, he will have to make that last line a statement rather than a question.)

I mentioned the mirror I just finished in the testing thread, and rather than divert that thread I figured I would start a new one. My mirror is a 10" f5.3. I started grinding in 6/03, polishing 10/03, and finshed figuring in 10/04. I figure I spent at least 100 hours with the pitch lap and the mirror lost almost four inches off its focal length from the time I started polishing till completion. All this polishing time went towards fixing two badly turned edges and many figuring attempts.

I have attached a composite image of the nine sets of foucalt data I have. The horizontal axis is the distance from the center of the mirror to the edge, and the vertical axis is the wavefront error. The vertical scale is different for each graph, but in each case the red line indicates a height of 1/10 wave (measured from the bottom of the chart). The first test I took is in the small graph at the bottom middle. I used a quick and dirty testing aparatus in my living room (it uses dental floss to measure the knife edge movement). After seeing this result, I figured I had better go to the mirror class that night (I was planning to skip it). At the class we took the remaining six sets of data at the top of the picture. The instructor and I each took one set of readings along three different diameters. My readings are on the left and his are on the right. The two readings taken at chabot are at the bottom.

The mirror star tests slightly undercorrected (bright outer ring inside focus and vice versa.) I find this somewhat puzzling as the center is clearly too deep and the majority of the tests suggests that the edge is also low. If I compare the star test images to Suiter's book, I can easily see that it is better than his 1/4 wave undercorrected image. However, it is hard for me to objectively rate how my images compare to his 1/8 image. My wishful eye is a big problem here, but I am also very green with the star test. I also have not had a chance to star test under favorable conditions.

Since I am leaving for two weeks on wednesday morning, today was my last (realistic) chance to get first light. I rushed out to the first semi-dark site I could find, but the moon was already starting to rise. I was not able to push the power due to the seeing, but I could easily tell that the light grasp simply blows away my current 6" newt. Given the amount of moonlight flooding the sky, I had some fairly impressive views of the veil and the orion nebula. I got a peek at saturn before I left, but the seeing was just too crappy to see much (anything below a 15mm EP was a waste of time.) Unfortunately my trip lasts just past the next new moon, so my next observing session will probably be under similar conditions. My first chance to really push this sucker will probably happen around the new year.